I know not everyone uses collections but i've seen many players have tons of collections including myself and it gets very messy. I think it would be useful to be able to have collections in other collections for better organization.
You mean like, you can have an "Anime" category,and have a tons of songs from many anime, many from the same, you can kinda connect them to the anime automatically? I made a small representation of what I mean (I made this in 5 minutes don't judge my graphic design skills) https://drive.google.com/file/d/1MKE04mfJ-jmEQm7TQ43Y5aKvlaeNPl3v/view?usp=drivesdk
Ok as i started grouping my maps now i get what you mean, this is needed fr. I added this on github so devs will be able to possibly read it
Edit 3: I decided that it will probably be faster to add this as a github post. Thanks to that the devs will be able to progress with this slightly faster, if this will be agreed on heres the link: https://github.com/ppy/osu/discussions/29390