Finished the output filename mask code, with the live demo of the mask in action and the file i/o fully tested. A couple of things remain:

• That popup menu is still in the wrong place.
• I haven't decided how to handle old Transformer files; if it's even possible to map the old setup onto the new, I should try it, but I should also warn people when they open an old file that they should review the filename settings.
• I probably haven't cleaned out all the obsolete messages stored in labels in the Batch form.

This stuff shouldn't take long, and then I'll be in a position to take on Transformer itself, starting with the data structure for replace items.