Rated 5 out of 5 stars

A very use-full extension! Thank God for the author. But where does it store the custom scripts? If anyone knows please respond.

This review is for a previous version of the add-on (0.3.2.1-signed). 

Check about:config and search for bbcodextra. For each custom tag you'll find two keys: extensions.bbcodextra.customX.action and extensions.bbcodextra.customX.label

Unfortunately I don't have time to work on this extension, and one of the features requested is to provide some way to import/export settings. Technically speaking you could do that just by copying the keys from one prefs.js to another, but that's become way too complicated since everything is hidden inside omni.ja