Found a new method of doing private or specific group calls in DMR mode. If you create your own Talk Group (TG) you can Key it active. Anyone else that keys up to that same Talk Group number will be able to chat with you.
They are calling it a Adhoc Talk Group.
I tested this with another Ham, we both created a TG 31000077, once you key it up, you have a private TG. If you want to make it a semi-private multi user group, just give out the TG number to other hams and you all have your own temporary TG.