How it works?

You can load non-tool script and directly instantiate them

tool_node.gd

@tool
extends Node

func _ready() -> void:
  	var node: Node = preload("res://my_node.gd").new()
    print(node.get_text())
    node.queue_free()

my_node.gd

extends Node

func get_text() -> String:
    return "Text from my_node"

Text from my_node

Using this it is possible to build a setup that will instantiate and copy data to it using get_property_list.

To get the placeholder you can use set_script

tool_node.gd

@tool
extends Node

func _ready() -> void:
  	var node_script: Script = preload("res://my_node.gd")
    var node: Node = ClassDB.instantiate("Node")
    node.set_script(node_script)
    print(node.get_text())
    node.queue_free()

my_node.gd

extends Node

func get_text() -> String:
    return "Text from my_node"

ERROR: res://tool_node.gd:8 - Invalid call function 'get_text' in base 'Node (my_node.gd)': Attempt to call a method on a placeholder instance. Check if the script is in tool mode.

You can still set their exported properties, be it directly or through get and set. So using this the data will be copied back