There are 14 MDD templates in ADL3 manager, some need extra transmitted channels some don't.
If you choose Orig ADL display then there are no extra transmitted channels and the MDD just displays what's set up to display on the ADL, on mine revs along the top, gear in the middle and a couple of temps, plus you get the alarm messages along the bottom.
If you choose horizontal graphs for example then you need to send ranges, max and mins and finally what parameters to display. I've set up both as examples and they work but I don't recall where I got the formats from. I'll have a hunt around.
Found them -
here.
The 8xEGT for example comes pre set-up with the ranges, max and mins already set up in the transmitted channels. So I think if you choose a template that comes without any transmitted channels included then you don't need any.
When you say you want the ADL to be in dumb mode have you already cleared off all the stuff in the ADL display set up? If so then that could that explain why your MDD is blank too, all working as intended. Doesn't explain the waiting for data message though.