When you have many Collections, it becomes harder to add a game to a specific collection as you need to find it in a dropdown that sorts them by most recent usage to oldest usage (i.e. if you’ve just added game to collection C, C appears on top), not alphabetically.

I see two ways to make this easier:

• make a hybrid search/dropdown field: type the beginning or part of the collection name to filter them out and possibly highlight the matching substring. Gamejolt does this when you click the + button “Add to Playlist”
• add a button on the Add to Collection popup to toggle Alphabetical sorting instead of Chronological usage sorting. Gamejolt always sorts alphabetically, which I find easier, but if you want to keep the chronological sort then the toggle is a nice solution. Alternatively for users who always use one or the other, you can add the toggle in the User Preferences. But you can have it in both places too.