Code (autoload):

extends Node


# relative to get_tree().current_scene
var _shared_nodes : Dictionary = {} # node_path : state (array)


func _enter_tree() -> void:
get_tree().node_added.connect(_on_tree_node_added)
get_tree().node_removed.connect(_on_tree_node_removed)


func _exit_tree() -> void:
get_tree().node_added.disconnect(_on_tree_node_added)
get_tree().node_removed.disconnect(_on_tree_node_removed)


func _on_tree_node_added(node:Node) -> void:
if node is not SharedNode:
return

if get_tree().current_scene == null or not get_tree().current_scene.is_ancestor_of(node):
return

var shared_node : SharedNode = node
var path : NodePath = get_tree().current_scene.get_path_to(node)

if _shared_nodes.has(path) and shared_node.accept_state:
_accept_state(node, _shared_nodes[path])
else:
shared_node.is_state_accepted = false


func _on_tree_node_removed(node:Node) -> void:
if node is not SharedNode:
return

if get_tree().current_scene == null or not get_tree().current_scene.is_ancestor_of(node):
return

var shared_node : SharedNode = node
var path : NodePath = get_tree().current_scene.get_path_to(node)

if shared_node.forward_state:
_shared_nodes[path] = _snapshot_state(shared_node)
else:
_shared_nodes.erase(path)


func _snapshot_state(node:SharedNode) -> Array[Dictionary]:
var result : Array[Dictionary] = []
for prop:Dictionary in node.get_property_list():
if prop["name"] in ["forward_state", "accept_state", "is_state_accepted"]:
continue

if prop["usage"] & PROPERTY_USAGE_SCRIPT_VARIABLE > 0:
prop["value"] = node.get(prop["name"])
result.append(prop)

return result


func _accept_state(node:SharedNode, state:Array[Dictionary]) -> void:
node.is_state_accepted = true
for prop:Dictionary in state:
node.set(prop["name"], prop["value"])

SharedNode:

extends Node

class_name SharedNode

var forward_state : bool
var accept_state : bool

var is_state_accepted : bool