You build a track, save it... ...oh no, wrong directory. Switching back to windows, searching the track within 40 others , copy, paste.
I don't know anything about the beta beyond the vids; here's my suggestion:
Enhancing the filesystem in Trackmania: Create/delete/rename Folders; searching (not sure if it's available in tm though); Copy, paste and all the other fun stuff a Explorer/Finder will enable us to do

Cheers
Nym