I have found that entering Document User Text keys via the Document User Text Panel at the right will not persist. It will allow me to enter a new key, even give it a value. Then if I go to connect that Document User Text key I made it is not in the list. If look back at the Document User Text Panel it is indeed gone.
I can repeat this over and over again as I have found that I can even watch the key I just made in the Document User Text Panel and as soon as I click the the function icon in the Properties Panel for the text object I want to connect to the key the Text Field window opens and the key I created disappears from the Document User Text Panel right before my eyes. Needless to say I don’t think it should work that way. I think that should be able to enter keys and values in that panel just like I can in Document User Text accessed from Edit→Settings. Another observation is editing the key of a previously entered key that was entered via the Document User Text from Edit→ Settings the edits do not persist either, they will revert back to what it had been prior to the edit, at least the key doesn’t entirely disappear in this case.
Regarding the same Document User Text Panel - it is kind of annoying that if you click the + to enter an item, then click the + again to enter another item you overwrite the item you just made so you must click some place else to finalize the entry then click the plus again to add another key. I think clicking the plus should finalize the last entry and start a new one, not overwrite the last one. Would have saved me dozens of clicks (and dozens more as kept trying to do it thinking I was screwing up something up somewhere) today as I unknowingly added items just to have all of them disappear as soon as I went to attach one of them to a text object.