...is there a way to force MusicBee to update an album folder path to the correct casing so future exports of the playlist will work correctly?
As far as I can work out the best way (or at least one way) to do this is to move the album to a new folder location and then move it back again.
Right-click > Send To > Folder (Move) > Move Files To Organised FolderSo, for your example, you might want to create a
Z:\Temp\ folder and then set the 'to folder' setting to 'Z:\Temp\' and the 'naming template' to '<Album Artist>\<Album>\<Filename>' (or however you save your files).
This should create a new folder structure with the correct capitalisation.
Then repeat the process to put it back using the 'to folder' setting 'Z:\M1\'
It's a little clumsy but I think it works.