Carolin_W

I see on mobile, product thumbnail show 1/2, you can add slideshow arrows, easier for users navigation to view more photos
Add this to Design > Custom CSS to add slide arrows
/* Product slide arrows control */ @media screen and (max-width:767px) { .ProductItem-gallery-carousel-controls { display: flex !important; } /* arrows background */ .ProductItem-gallery-carousel-controls * { background: white; } .ProductItem-gallery-carousel-controls>div { justify-content: center !important; } .ProductItem .ProductItem-gallery-carousel-controls>div::after, .ProductItem .ProductItem-gallery-carousel-controls>div::before { border-color: black !important; } }  

Try adding to Design > Custom CSS
.ProductItem-details-checkout { display: flex !important; justify-content: center; align-items: center; }  

The code @tuanphan posted was for a Squarespace v7.0 site. Your site is v7.1 and requires different code.
Add the following to Store Settings > Advanced > Page Header Code Injection.
<style> /* There is something odd going on with v7.1 CSS as of 11/04/20 .ProductItem-details-checkout has a rule of display block but sub elements have order properties on them. The first bit of CSS unsets those items for a clean slate returning the elements to natural order. */ .ProductItem-details .product-quantity-input, .ProductItem-details .product-variants, .ProductItem-details .ProductItem-details-excerpt, .ProductItem-details .ProductItem-product-price, .ProductItem-details .sqs-add-to-cart-button-wrapper { -webkit-box-ordinal-group: unset; -ms-flex-order: unset; order: unset; } .ProductItem-details .product-variants { -webkit-box-ordinal-group: 8; -ms-flex-order: 7; order: 7; width: auto; } .ProductItem-details .ProductItem-details-excerpt { -webkit-box-ordinal-group: 9; -ms-flex-order: 8; order: 8; } .ProductItem-details .ProductItem-additional { -webkit-box-ordinal-group: 9; -ms-flex-order: 8; order: 8; } @media only screen and ( pointer: coarse ) and ( min-width: 1025px ), screen and ( min-width: 800px ) { .ProductItem-details .ProductItem-details-checkout { -webkit-column-gap: 3vw; -moz-column-gap: 3vw; grid-column-gap: 3vw; column-gap: 3vw; display: -ms-grid; display: grid; grid-row-gap: 3vh; row-gap: 3vh; -ms-grid-columns: 1fr 3vw 1fr 3vw 1fr 3vw 1fr 3vw 1fr; grid-template-columns: repeat( 5, 1fr ); } .ProductItem-details .ProductItem-details-checkout > * { -ms-grid-column: 1; -ms-grid-column-span: 5; grid-column: 1 / 6; margin: 0; margin-right: 1vw; } .ProductItem-details .product-quantity-input { -ms-grid-row-align: end; align-self: end; -ms-grid-column: 1; -ms-grid-column-span: 1; grid-column: 1 / 2; margin-right: 0; } .ProductItem-details .sqs-add-to-cart-button-wrapper { -webkit-box-align: center; -ms-flex-align: center; align-items: center; -ms-grid-row-align: end; align-self: end; -ms-grid-column: 2; -ms-grid-column-span: 4; grid-column: 2 / 6; width: auto; } } @media only screen and ( pointer: coarse ) and ( max-width: 1024px ), screen and ( max-width: 799px ) { .ProductItem-details .ProductItem-details-checkout { display: -webkit-box; display: -ms-flexbox; display: flex; } } </style> Let us know how it goes.

Some CSS Class/ID for Squarespace 7.1
Announcement Bar
Announcement bar: .sqs-announcement-bar-dropzone Announcement bar text: .sqs-announcement-bar-dropzone p Announcement bar link: .sqs-announcement-bar-dropzone a Announcement Bar Close Icon: .sqs-announcement-bar-close OR .sqs-announcement-bar-close:after Header
Header: header#header Sticky Header: header.shrink Header (not include sticky header): header#header:not(.shrink) Header (when burger menu is open): body.header--menu-open header#header Header (when burger menu is close): body:not(.header--menu-open) header#header Site Title: a#site-title Site Title (when overlay menu open): .header--menu-open a#site-title Site Title (when overlay menu close) body:not(.header--menu-open) a#site-title Navigation: .header-nav Navigation Items: .header-nav-item a Navigation First Item: .header-nav-item:nth-child(1) a Navigation Second Item: .header-nav-item:nth-child(2) a Navigation Dropdown: .header-nav-folder-content Navigation Dropdown Items: .header-nav-folder-item a Navigation Folder Title: a.header-nav-folder-title Mobile Navigation Items: .header-menu-nav-item a Mobile Navigation First Item: .header-menu-nav-folder[data-folder="root"]>div>div:first-child Mobile Navigation First Item (text): .header-menu-nav-folder[data-folder="root"]>div>div:first-child a Mobile Navigation Second Item: .header-menu-nav-folder[data-folder="root"]>div>div:nth-child(2) Mobile Navigation Second Item (text): .header-menu-nav-folder[data-folder="root"]>div>div:nth-child(2) a Mobile Menu Icon: .header-burger Mobile Burger 3 lines: .burger-inner>div Mobile Menu X icon: body.header--menu-open .burger-inner>div Header Social Icons: .header-actions .icon Cart Icon: header#header span.Cart-inner Cart quantity: header#header .icon-cart-quantity Header Button: header#header a.btn Header Desktop Button: .header-display-desktop a.btn Header Mobile Button: .header-menu-cta a a Footer
Footer: footer#footer-sections Footer Social Icons:  footer#footer-sections  .sqs-svg-icon–outer Footer Links: footer#footer-sections a Product List
Product List: .collection-type-products.view-list Product Name: .grid-title Product Price: .grid-prices Product Image: figure.grid-image Product Currency: body.native-currency-code-usd .sqs-money-native:before Sold Out Text: .product-mark.sold-out Product Detail
Product Detail: .collection-type-products.view-item Product Breadcrumb: .ProductItem-nav-breadcrumb Product Pagination (Previous/Next): .ProductItem-nav-pagination Gallery: figure.ProductItem-gallery Thumbnails: .ProductItem-gallery-thumbnails Big Image: .ProductItem-gallery-slides Product Name: h1.ProductItem-details-title Price: .ProductItem-product-price Currency: body.native-currency-code-usd .sqs-money-native:before Excerpt: .ProductItem-details-excerpt Add to Cart Button: .sqs-add-to-cart-button-wrapper Add to Cart Text: .sqs-add-to-cart-button-inner Variant Dropdown: .variant-option Variant Title: .variant-option-title Variant Options: .variant-select-wrapper option Quantity Text: .quantity-label Quantity Input: .product-quantity-input Cart Page
Cart Page: body#cart Cart Page Title: .cart-title Product Name: a.cart-row-title Product Thumbnail: div.cart-row-img Qty minus: .cart-row-qty-dec Qty plus: button.cart-row-qty-inc Qty number: input.cart-row-qty-input Price: .cart-row-price X icon: .cart-row-remove or .cart-row-remove svg Sub total text: .cart-subtotal-label span Sub total price: .cart-subtotal-price Checkout Button: button.cart-checkout-button   Item: .CartTable-itemLabel-3zzV1 QTY. .CartTable-itemLabel-3zzV1 span Price Name: .CartTable-itemPrice-XgjsO span X icon: .item-remove div Blog List
Blog List: [class*="type-blog"].view-list Thumbnails: article.blog-item img Date: time.blog-date Category: span.blog-categories-list Title: h1.blog-title Excerpt: .blog-excerpt Read more: a.blog-more-link Blog Posts
Blog Posts Page: [class*="type-blog"].view-item Blog Items: .blog-item-entry Categories: .blog-meta-item–categories Date: time.dt-published.blog-meta-item.blog-meta-item–date Author: .blog-meta-item.blog-meta-item–author.p-author.author Title: .blog-item-title Content: .blog-item-content-wrapper Pagination: .item-pagination Pagination Arrows: .item-pagination-link .item-pagination-icon Pagination Title: h2.item-pagination-title Author Box: .blog-item-author-profile-wrapper Author Image: a.author-avatar.content-fill Author Name: .author-name Author Site: a.author-website Post Comment: .squarespace-comments Post Comment Button: .comment.btn Comment Input: .squarespace-comments .new-comment-area Preview: span.btn-text.preview-comment.top-level-preview-btn Subscribe via email text: span.subscribe.subscribe-control Blog Grid
updating
Blog Masonry
updating
Event List Page
Event List Page: .collection-type-events.view-list Event Thumbnail: a.eventlist-column-thumbnail.content-fill Event Time: .eventlist-datetag Event Date: .eventlist-datetag-startdate.eventlist-datetag-startdate–day Event Month: .eventlist-datetag-startdate.eventlist-datetag-startdate–month Event Title: h1.eventlist-title Event Hour: li.eventlist-meta-item.eventlist-meta-time.event-meta-item Event Description: .eventlist-description Event Detail Page
Event Detail Page: .collection-type-events.view-item Event Title: h1.eventitem-title Event Date: time.event-date Event Hour: li.eventitem-meta-item.eventitem-meta-time.event-meta-item Event Description: .eventitem-column-content Event Pagination: section.item-pagination.item-pagination–prev-next Previous/Next: .item-pagination-link .item-pagination-prev-next Event Pagination Title: h2.item-pagination-title Portfolio
title: h3.portfolio-title item: .portfolio-grid-basic portfolio image: .portfolio-grid-basic .grid-image pagination: [data-collection-type=“portfolio-grid-basic”].item-pagination pagination text: h2.item-pagination-title pre text: .item-pagination-link–prev .item-pagination-prev-next next text: .item-pagination-link–next .item-pagination-prev-next List Simple
List Simple: .user-items-list-simple Image: .user-items-list-simple img First Item: .user-items-list-simple li:nth-child(1) Second Item: .user-items-list-simple li:nth-child(2) List Content: .user-items-list-simple .list-item-content Title: .user-items-list-simple h2.list-item-content__title Description:  .user-items-list-simple list-item-content__description OR .user-items-list-simple p List Slideshow
List Slideshow: .user-items-list-banner-slideshow Image: .user-items-list-banner-slideshow img First Item: .user-items-list-banner-slideshow li:nth-child(1) Second Item: .user-items-list-banner-slideshow li:nth-child(2) List Content: .user-items-list-banner-slideshow .slide-content Title: .user-items-list-banner-slideshow h2.list-item-content__title Description:  .user-items-list-banner-slideshow list-item-content__description OR .user-items-list-banner-slideshow p Arrow Circles: .user-items-list-banner-slideshow .user-items-list-banner-slideshow__arrow-button Arrow Icons: .user-items-list-banner-slideshow .user-items-list-banner-slideshow__arrow-button svg Button: .user-items-list-banner-slideshow .list-item-content__button List Carousel
List Carousel: .user-items-list-carousel__slides Image: .user-items-list-carousel__slides img First Item: .user-items-list-carousel__slides li:nth-child(1) Second Item: .user-items-list-carousel__slides li:nth-child(2) List Content: .user-items-list-carousel__slides .list-item-content Title: .user-items-list-carousel__slides h2.list-item-content__title Description:  .user-items-list-carousel__slides list-item-content__description OR .user-items-list-carousel__slides p Arrow Circles: .user-items-list-carousel__arrow-button Arrow Icons: .user-items-list-carousel__arrow-button svg Button: .user-items-list-carousel__slides .list-item-content__button Fluid Engine
Fluid Block (text block, image...): Each block is wrapped by the same class name .fe-block and a unique id. And All .fe-blocks will be wrapped by a parent tag with a class name of .fluid-engine
 
Checked & Wrote by tuanphan

I did the same this past month because it's utterly ridiculous that it's not included in the 'new' hype version, and was told the same. But someone on mgmt did reach out, though they didn't make any promises. It's a pain in the butt. I was also asking about recipe inserts - you know the easy inserts where people can print the recipe if they want? For blogs this is all fairly basic functionality and options. Not the kind of thing I want to be paying for and not have.
 

What's even more confounding, is that the controls are there. They simply don't work as yet. Social sharing is such an integral part of marketing for most of us, and it would seem to me that implementing this function should have been at the top of the list of things-to-do for the Squarespace team.