Firstly forget about scenes
and scripts
those are terms used in the Editor portion of Godot.
During gameplay each node in the sceneTree is considered an instance
and has a unique nodepath, instanceID and name
Each variable in the script attached to a node is called a member
during runtime and can be accessed as well as functions from that node if referenced using one of the previously mentioned unique ways
Let's say you have this sceneTree
┖╴root
┖╴Maingame
┠╴HITBOX(Area2D) [Hitbox Script]
┃ ┖╴Node2D
┖╴PLAYERSTATS (Area2D) [Player Stats Script]
┖╴Control
Once you have the reference to the PLAYERSTATS node
onready var stats_values = get_parent().get_node("PLAYERSTATS")
you can access or change all of it's members directly by using that variable with .member_name
Example
damage = stats_values.damage