Hi.
Having filters running, they run always, e.g., sorting away emails into subfolders.
Catch: If you have thunderbird running on your desktop, you'll may miss messages on your mobile, because they are sorted away from your inbox instantly. On the other hand, not having a filter means, you have to do the sorting manually yourself, which may be tedious.
Proposition: Have the possibility of (a customizable number of) buttons, say on the left window side, maybe in the spaces toolbar, that have customizable filter actions "attached" to them, that are applied to the currently open message only (not to the entire folder, like ordinary filters).
I'd assume, these buttons could be useful for a number of workflows.
PS: And while we are at it, have the option to have keyboard shortcuts for these buttons, so that these actions may even be executed from the keyboard. I could think this helps getting through your inbox fast.