Adding Pinterest Metadata

I have enabled rich pins so that when people pin images from my blog using my Pinterest Save Button, it fills in all the extra metadata from Squarespace, like the post title, post description, alt text, etc. I used this article to do it: https://thirtyeightvisuals.com/blog/pinterest-rich-pins-squarespace?fbclid=IwAR3MihzgrQd1XZXzwaOL5uoOftb4gzWsqe8oW-6CHzcgmhzVrk16fcKL9wA

It works kind of well. Sometimes certain pins don't follow the rules. Like, in that link she shows how to make the author default to "My Name | My Blog Name" instead of simply "My Name". It only works about half the time; some pins will say the correct author and other pins still just say "My Name". Whatever, I can deal with that. Sometimes the title is not the blog title like it's supposed to be, which is a little more annoying, but it's an infrequent problem I can also deal with.

But, I want to be able to change the description. Using the above, the main description defaults to my blog post description, and the secondary description defaults to my image alt text. Leaving alt text as-is is fine, but for the main description I want to create my own special description for the pin, mainly because some of my blog post descriptions are really long, I'd like the pin description to be more succinct without having to change my blog post description. Also I want to add hashtags to my pin description. I know on Wordpress they can edit data-pin-description, alt text, data-pin-title, data-pin-url, data-pin-media, etc etc when they upload an image. Squarespace users have no automated way of doing this, but I figured there must be a way to do it manually.

So then I found these instructions: https://www.untangledbiz.com/blog/2018/11/7/why-alt-text-not-the-right-place-for-pin-descriptions

This also....kind of works. I can put in the correct image and URL, but none of the other metadata tags populate correctly. Data-pin-description fills in the secondary description that's in small text at the bottom (which is usually just the image alt text), instead of the main description. What I'm wanting to edit is the main description. Using "alt="insert alt text here" doesn't work at all to change the alt text area back to what it's supposed to be. Data-pin-title doesn't work at all either, it's still defaulting to the blog post title. (This is a brand new tag Pinterest is implementing so maybe I shouldn't expect data-pin-title to work yet, but my Wordpress friends have gotten it to work).

Any other ideas? How can I change my pin descriptions to something custom instead of just the blog post description? Doesn't seem like it should be this hard. Should I just give up and accept whatever the rich pin format gives me?