Maybe this is already the case, but it is not obvious.
The list of "favorite folders" should be in priority order, as I might have multiple folders in there.
Thus, you would need to be able to change the priority order of the folders. The typical way is to have UP and DOWN buttons which move the selected item in the list higher or lower in the order.
Thus, the higher the folder is in the list, the more it's files are preferred.
Question: what happens if there is a BETTER file (ie higher bitrate) in a LESS preferred directory?