@Jason Carr The bigger problem was getting it to recognize that roms had been removed, not added. For example, when I removed roms that weren't part of the no-intro set. Until I found "scan for removed roms" the only way to do this sanely was to delete the platform and re-import, which is also a big metadata download.
Tangentially, though, it would be nice if I could use the audit tool to import into an as-yet not-autogenerated platform. For example, I'm about to split my NES platform into NES and Famicom. If I import a game as a Famicom game, it auto-populates a default platform to use; but if I use the audit tool to bulk-edit all my (Japan) NES games from NES to Famicom, I have to manually define the Famicom platform.
I'd say it should behave more like the emulator interface, where if you create a Retroarch emulator it auto-populates with default cores for each platform. That wasn't terribly discoverable, but at least it worked.
Unless I'm missing something. Like I said, I'm new to LaunchBox.