0.9 Introduced the ability to run your own scripts inside the editor, this is a much more advanced alternative to the Expression Runner.

Basics of scripting are included in the file that gets created when you add a new script, class reference is available below.

Please also read the GDScript Documentation:

https://docs.godotengine.org/en/stable/getting_started/scripting/gdscript/gdscript_basics.html

Additionally, any GDScript built-in is available to use:

https://docs.godotengine.org/en/stable/classes/[email protected]

Keep in mind, all timing points inherit from HBTimingPoint, and all notes inherit from HBBaseNote