So I noticed, if achieved, achievements are sorted (per game) by the time you achieved them. But if not, it seems like they're all over the place. As most platforms have a certain order in which achievements are shown, I'd like for GOG to transfer that order. Maybe give us options to sort them like 'standard' for what I just described and 'time' for like it is now.

Also another thing about achievements, especially PS4 trophies:
I got some collections of multiple games. When playing, PSN only shows that I'm playing the collection, not the exact game. BUT it shows the achievements separate for each game in the collection instead of mashing them all together in one big list. I'd love to see that (at least for platforms supporting this like PS4) on GOG aswell :)

For example, I own Kingdom Hearts - HD 1.5+2.5 ReMIX. This contains 4 games:
1) Kingdom Hearts Final Mix
2) Kingdom Hearts Re:Chain of Memories
3) Kingdom Hearts II Final Mix
4) Kingdom Hearts Birth by Sleep Final Mix

I added a picture of how PSN manages this for reference.
Same goes for 'Kingdom Hearts 2.8', 'Kingdom Hearts The Story So Far' and 'Journey - Collector's Edition', multiple games with separate achievements.

Edit: Oops, wrong picture. Seems like I can't edit that, so here's the right image: https://imgur.com/FTkauc8

+1

Let me add that it would be nice to sort unachieved ones by difficulty (start with most common, end with the rarest) like it's used on steam