Even with deleting all unused characters on a monthly basis, I often find myself with a dozen character sheets. It's not difficult to find the character sheet I'm looking for, sure, (mostly because I delete the excess before I reach 30,) but wouldn't it be nice to have folders or a custom priority order?

A folder system is pretty self evident, so I don't have to elaborate on that.

A custom priority could allow users to mark their characters that are actually in a campaign as important, preventing them from almost accidentally purging them, as well as allowing them to be found easier. This could be as simple as a single priority tag that puts them before any unprioritized sheets in the list, or a priority system, where you can manually assign importance on a scale. Example: Favourite character gets 1, main backup 2, Fun but not quite ready concept 3, That old character with fond memories 4, etc. Making another character sheet number 2, for example, would push the old 2 to 3, the old 3 to 4, and so on.

The system doesn't need to be as complicated as what I just described, but some controlled sorting system would be very nice to have.

 Custom prioritization can easily be done by sorting alphabetically and using emoji or special characters or numbers.

I'm not against folders, but I must point out that any character in a campaign has that campaign listed in red beneath their name/race/class AND you can get to those characters through the My Campaigns tab as well.