There is a save feature, that little star icon. I just tried it and it gets saved on your profile it looks like. It works for both posts and comments.
I use Gamefaqs and MobyGames to track my collection. On Gamefaqs there's a lot of ways to categorize games like digital/physical and played/finished and more. MobyGames looks nice and both of these are games database websites so they also have tons of other info so I also just browse and find info about various games/companies/people etc.
It seems most Steam users still prefer to buy games instead of using Gamepass. Microsoft made a push to get more PC Gamepass subscribers(they had a promotion with friend trials, might still be going) since there's huge potential for growth but I'm not sure how it's going.