Deleting the last.yourinterface.xml worked, I can use totalmix again, nice. You didn't mention that the snapshots are deleted, too, but I could take an older last.yourinterface.xml from a backup.
By the way - when I quit totalmix, is there a trick to open it again without restarting the computer? When totalmix has been closed, it is not in the task bar / system tray any more. When I search for totalmix in the start menu there is no result, and I don't see it in program files or programs (x86).
Apple 16" MacBook Pro M1Max 10Core 32GB RAM; RME fireface 800; Behringer ADA8200; Line6 Helix)