How to delete files from MPC KEY 37/61 internal drive?

Hi. I can't find any way to delete project files (or any file) from the internal SD drive (OS 3.5).
I read the MPC Bible and the manual. There seems to be no way to do it? The files FAQ section mentions copying & deleting files, but doesn't show how.
Any help would be appreciated. thx

Only delete Project files you created. Do Not Delete any Pre-loaded Files.

Browser
highlight the settings tab to "See Hidden Files"
Then go to your Project Folder and delete the XPJ and the Data File for each Project