Red Alert appeared: Maximum number of files. Delete some ... what & where?

Moving along very nicely, when the system started to bog down, then crashed twice, and finally, I just now received a Red Button Alert, telling me that Audition had reached the maximum number of files, and I need to delete some.  It is not saving my edits now. 

I have my main multi-track session files on a removable 2TB, pretty well organized in folders with all their referenced files enclosed.  All files are in the same folders with their sesx file.  I  then exported to WAV, and have been working through those files pretty successfully for a week now.  But obviously, the back-up and demands on the application have created this impasse.

I am delving into the User Guide, but can anybody send me in the right direction?

I have my files backing up to a removable 2TB drive, which currently has 94 GB free.  I have set a secondary back-up on Creative Cloud, and 12.63 GB in my Audition folder inside my system folder. of files in the Audition folder on my internal Hard Drive.

Maybe useful -- to me the stuff of nightmares -- screenshots from my Audition Preferences backup locations,  along with the Info on my main (UFI) hard drive, and the removable (UF-006) 2 TB drive.   

I just need to know what I can SAFELY delete to get back to work.   

Thanks for any help.

rob