I'd like to put this out there I'm on Brine 7.0, this code is written by Ryan Dejaegher for Squarespace 7.1
I liked it so much I took a chance and injected it into a code block!!! AND IT WORKED!!! Even better it works on independent pages too. Ryan offers this code FREE from one of his blogs, I'm not affiliated with Ryan, I just thought I'd put it out there for all to see!
Settings -> Advanced -> Code Injection -> Footer
<script src="https://cdn.jsdelivr.net/gh/ryandejaegher/vertical-nav@0.0.5/script.js"></script>
<vertical-nav side="right">
<a href="#">First Link</a>
<a href="#">Second Link</a>
<a href="#">Third Link</a>
<a href="#">Fourth Link</a>
</vertical-nav>
Please note I am not a web designer or a coding genius, I just like to play around pimping my site and learning.
I think you'll agree with custom icons thrown into the mix side nav looks pretty cool huh? https://fit4thepart.com/new-page-from-wavy-click-thru#what
Place the code in FOOTER from site-wide, or target per page for even more custom options, you could even insert "left" or "right" into the code for side navigation position, get the code here https://ryandejaegher.com/add-fixed-vertical-navigation-to-squarespace/
Shout out to CANVA for the icons https://www.canva.com/