Thanks for pointing this issue out - I’ve been able to reproduce it, and have passed it to the development team for further investigation. As a workaround, you may wish to try using studio.system.start() or studio.system.startAsync() to create a folder in the asset folder via the appropriate filesystem command, which should be get picked up by FMOD Studio’s asset browser.
My apologies - the folder will only be automatically added to the asset browser once it contains an audio file of some kind. Beyond that, I can’t offer any further workarounds.