I´ve been trying to use the onshutdown functionality, but I didn´t get to make it work.

I’ve been trying to make persist ome data to a NEW SQUIRREL SHUTDOWN . But I press the “run” button and the imp don’t execute the onshutdown call.

What am I doing wrong?

This API is not called by the system yet. You should just persist data when you need to (ie, when it changes).