What you probably SHOULD be doing is some sort of class system. I am not sure what your scripts are doing, but if you want some of them to share functions and then want those functions to change, make a class_name script with those base function and then write new scripts to each object so you only inherit what you need. For example, let's say you have a door object that opens and closes:
extends Area2D
class_name DoorDefault
func _open():
##### some function here
func _close():
#### another function here
An advantage of this is then when you create new scenes, you can have them start with this script attached. Then you're not repeating code.
Then in inheritors:
extends DoorDefault
func _custom_function():
### custom function here
One caveat of this: be careful that you don't run into the "Deadly Diamond" of inheritance, where two nodes inherit from one node, then another node inherits from those because this can cause a LOT of problems. (Example: A inherited by B and C, then D inherits B and C.)