how making a custom script or a little example for a beginner?

make the script in the js, or use the defaults expressions of mosi, make new scripts?

Trying transform a sprite in other room! .
I tried various combinations with the normal scripts and they did not work.

Custom scripts are javascript functions that take in the world state as an argument, and return an updated world state. I haven't really documented custom scripts thoroughly because I think the best way to understand how they work is to take a look at the script.js source code and see how I've implemented the built-in scripts.