Does anything know of a theme or app that has this built in? I’ve been looking for hours for something that can replicate the functionality shown in this video: MAHA Official Merchandise Store – Official MAHA™ Merchandise Store
Thanks in advance 
It’s just any recently-viewed/recommended section absolutely positioned to be the viewport height with a button to toggle the position.
Simple first then compound.
Try just asking the “AI” in the theme editor to make that section but might have problems with the compounded requirements of styles, interaction, and cookies/local-storage/cart-attributes.
Or reach out if you need it built/fixed.
I was able to hash it out that way - thank you!