Just uploaded version 0.32 as a beta to the Play Store with the following (should be available very soon):
Custom emulators are now supported, if you have the correct metadata for them (package name, activity name, and ROM path key)
Added support for over 50 new emulators!
The reason this release is going to beta first is that I honestly have not tested all 50 new emulators. I'm doubtful that we'll be able to test all 50 of them before making it an official release, but anything that we can test would be great. If anyone tests any of the new (or old) emulators and can confirm yay or nay, please comment here in the thread.
As a reminder, in order to download the beta version, you'll need to opt-in to beta releases here:
https://play.google.com/apps/testing/com.unbrokensoftware.launchbox
Then you should be able to update to the beta release on your device. Happy gaming.