My 3D Prototype SystemControl.gd code as of Jan 20, 2023

extends Node

#The Data System used is designed for my 3D Diary application.

#Data setup
const SAVE_DIR = "user://saves/" #This is useful for HTML5 as well.

# Called when the node enters the scene tree for the first time.
func _ready():
    pass # Replace with function body.

func _input(event):
    if event is InputEventKey:
        if event.scancode == KEY_F11 and event.echo == false and event.pressed:
            OS.window_fullscreen = !OS.window_fullscreen

func _ensure_directory_exists(path: String) -> void:
    var dir := Directory.new()

    if not dir.dir_exists(path):
        var __ = dir.make_dir_recursive(path)

#Loads a game, or can be used to load old data so it can insert with new data.
func _load_or_default(path: String, default: Dictionary) -> Dictionary:
    var file := File.new()

    if not file.file_exists(path):
        return default

    var error := file.open(path, File.READ)

    if error == OK:
        #var data = file.get_var()
        #file.close()

        #2. Create a file
        var save_file = File.new()
        save_file.open(path,File.READ)
        var data = parse_json(save_file.get_as_text())

        return data

    else:
        print("ERROR LOADING: %s" % error)
        return default

func save(SAVE_PATH, index, value):
    _ensure_directory_exists(SAVE_DIR)
    var original_data = _load_or_default(SAVE_PATH, {"default_data" : "to prevent any data glitches or data not found error if data is empty at start. That's why this note here exist."})

    var data_dict : Dictionary = {}
    data_dict[index] = value

    var overrides : Dictionary = data_dict
    var new_data := merge(original_data, overrides)

    #2. Create a file
    var save_file = File.new()
    save_file.open(SAVE_PATH,File.WRITE)

    #3. Serialize the data dictionary to JSON
    var save_string = JSON.print(new_data, "\t")
    save_file.store_line(save_string)#Godot 3 Code (based from another sample from data.gd)

    #4. Write the JSON to the file and save to disk
    save_file.close()

# Put this in some Dictionary helper class.
static func merge(left: Dictionary, right: Dictionary) -> Dictionary:
    var merged := {}

    for key in left.keys():
        merged[key] = left[key]
        print(merged[key])

    for key in right.keys():
        merged[key] = right[key]

    return merged


#Data for objects, items, furnitures.
func save__data_style1(SAVE_PATH, value):
    _ensure_directory_exists(SAVE_DIR)
    var original_data = _load_or_default(SAVE_PATH, {"default_data" : "to prevent any data glitches or data not found error if data is empty at start. That's why this note here exist."})
    #print(original_data)
    var data_dict : Dictionary = {}
    #data_dict["data_style1"][selectedObject][index] = value
    data_dict = value

    var overrides : Dictionary = data_dict
    var new_data := merge1(original_data, overrides)

    #2. Create a file
    var save_file = File.new()
    save_file.open(SAVE_PATH,File.WRITE)

    #3. Serialize the data dictionary to JSON
    var save_string = JSON.print(new_data, "\t")
    save_file.store_line(save_string)#Godot 3 Code (based from another sample from data.gd)

    #4. Write the JSON to the file and save to disk
    save_file.close()

# Put this in some Dictionary helper class.
static func merge1(left: Dictionary, right: Dictionary) -> Dictionary:
    var merged := {}

    for key in left.keys():
        merged[key] = left[key]

    for key in right.keys():
        if key != "data_style1":
            merged[key] = right[key]
        else:
            #print(right)
            for key1 in right[key].keys():
                merged[key][key1] = right[key][key1]
                #for key2 in right[key][key1].keys():
                #   merged[key][key1][key2] = right[key][key1][key2]

    return merged