No worries. I never got an answer in here before and honestly glad Im not the only one running into the issue.
FWIW I also emailed SideFX about this also and got this response:
Hello Ryan,
If you want to use the white selection arrow button, you’ll need to replace the script in the script_action tag. These scripts tend to be highly context dependent, and I’m guessing that the current tag was just copied by dragging a group field with the white selection arrow button into the Edit Parameter Interface. The main function being called, soputils.selectGroupParm(), takes a dictionary of arguments to control how it operates. Since I don’t think it’s possible to edit multi-line scripts in the Tags list UI, the easiest way is to just set your script_action tag “kwargs[‘node’].hdaModule().scriptFunction()” and then define this scriptFunction() in your HDAs PythonModule.
You can take a look at the source for soputils.selectGroupParm() in $HFS/houdini/python2.7libs/soputils.py for things that function tries to do and the arguments it expects. You can set kwargs[‘nodepath’] to the path of the node from which you want to select, or set kwargs[‘node’] to point to a node from whose input you want to select and kwargs[‘inputindex’] to specify which index.