I have my doubts about this actually being implemented. No UMA folder exists, and the last comments I see on this go back to threads about it being implemented in 2016, with no follow-up.
I will say that I was able to get things rolling by following the instructions here:
I have yet to try a profile capture using my old template, but will report back with results when i do.
Could you post up the sample xml? I've checked on my test cores and I can't find this file. I have a "SampleProfileXML.xml" on my 2017.3 core in the \ldlogon\uma\commandxml folder, but this doesn't light up the edit button. Copying this file and renaming it to "sample_command_file.xml" didn't light it up either.