I just tested custom sorting and custom tags for you, and it works.
I labelled custom tag 3 as 'Type' in preferences -> tags (1)
I have seven ACDC albums. In the tag editor I labelled a bunch of songs as 'singles' and one album as 'EP'.
Then I created a custom sort by right-clicking a column in the main panel -> sort by -> define custom sorting.
I used the following parameters:
Year <--- I like to have material listed in chronological order, but you don't need that.
Using this sort, the Albums came first, then the EPs, then the Singles (ie. alphabetical - A, E and then S).
There isn't a way to change that; it can only be alphabetical.
This does mean that you'll have to tag all your Singles and EPs as such, but I don't really see a way to avoid that - there's no
other way MusicBee could know if tracks are albums, EPs or Singles.
Hope that helps.
Just to note, I hate dozens or hundreds of singles being listed on their own.
So I usually collate all my singles, demos, EPs, etc into little collections as if they were an album.