Found a kludgy workaround that's almost does what I need...
Went to 'options', set ballooning to use "part name" instead of "numbers". Then once you create the balloon, you can set the "frame" to be "none" so the circle disappears.
Shortfalls...the leader anchor is in the middle like a balloon instead of the end like a text leader, and you only get a single line text editor instead of multi-line like a leader. The upside is you can quickly call out parts, and it's associative.
I still wonder if there is a way to put the correct variable name directly into a text leader?
Bueller...?