It would be so helpful if we could add achievements to our own in progress list so we know what ones we want to work on first from all catagories instead of having to go through each one. There could be a little plus mark by each achievement description so we could add to our own list.

This already exist actually! You can tick the box next to the achievement name, and then see the achievements you ticked on the Saved category, under the Newest one.

I thought that was what it might be for but when I check the box it just says "Unable to find those achievements :(". Is it something they are still working on perhaps?

That's weird, it seems to work fine for me. It was added some time ago, but I wouldn't be surprised if it's still full of glitches :c

I shall keep trying it later. Thank you. =)