Google Sheets - Menu Click Function in Library

Question

I have gsheet menu item as follows, where the executing function resides in library "rm".

ui.createMenu('Test').addItem('Test-Lib', 'rm.test');

I have tested this and it works. However, I was not able to find any documentation on this. So my question is; is this a supported feature which I can rely on going forward?

The use case here is: I will be distributing copies of the same gsheet to different clients, so having a single code repository helps updating all clients at the same time. -