Okay, turns out the only thing I really needed to change (on Poser 12.0.500) was the import wxPrepare in WXTools.py to import local_libs.wxPrepare. When loading the script I get an error complaining about a checkbox event with no object that I ignore, then the GUI for the tool appears and I only have to move it to a spot where I can see everything.

I have now managed to import a morph from an OBJ file using the tool. Do I understand correctly that I have to export the unmorphed figure each time directly before I import a new morph? Why is that necessary? I'm assuming some weirdness of the Poser interface?

-- I'm not mad at you, just Westphalian.