Natively, you can add a folder to the favorites bar and move by pressing ⌘ ⌃ 1 - 9 (according to the position of your favorite folder on such bar).
If you want to take it further (such as using more than the available numbered slots on Mail favorites), then you will have to look into something like Keyboard Maestro conflict palettes (as @MacSparky suggested in a recent webinar). If you want to go this way, then this can help you implement it.