Unfortunately, zenAud.io doesn't currently support this. It's something that we intend to support, and I'll probably on this on another thread.
There are two "workarounds"
- Deleting tracks is considerably faster using the keyboard. Type t and then hit the backspace key to delete tracks. (Usually backspace deletes regions/loops in the current track.)
- Create a song with your default routings, tracks, etc. but without any loops. Save it as "My Rig". Then, you simply open that song instead of the default song and then use Save As. It's not ideal.... but if your setup is more complex then this is probably faster.