Hi Nate,
I tried your way, but when I opened the GND2.dwg file, I can't find "TAG1" attribute, there is no block defined in that drawing, only a ground symbol (3 lines) and "X2TERM01", I delete that one, recreate by using "MISC/BLK", defined the symbol as a child, saved as HGND3.dwg.
After insert that symbol, when I automatically generate the wire numbers, it began searching the entire project to find out a parent symbol, after nothing find out, it generate a number, not "GND".
Did I do something wrong?
By the way, I cannot define the default value for the wire which will connect to the ground symbol.
I'm looking forward your reply. Thanks.