In the Loops picker where you have optional
"If you want a different sound for the ‘b’ substyle, enter that WAV file name in the "b substyle loop" setting."

You can have Endings with:
"If you want a one shot loop for the ending, enter that WAV file name in the "Ending loop" setting.
Or an A or B Ending loop option.

I bought some loops from SessionBand and they have Holds and Stops.
So maybe there's another option you can add.

Attached Files (Click to download or enlarge) (Only available when you are logged in)
SessionBand-Loops-Holds.png (72.44 KB, 30 downloads)
BB-LoopPicker-Ending-Hold.png (243.24 KB, 30 downloads)