What I'm looking to do is make a Doom/Duke Nukem-Like game.

I want the game to not only load maps that are already created, but to allow players to build their own maps right within the game.

What I'm having an issue with is how best to create/modify/store that map information with Godot. I'd like to be able to switch between editor and "game" mode with the same map. Off the top of my head, given I'm looking for persistent data between what would be two (or more) separate scenes, that sounds like I'd want to write the map "class" within an Autoload script. Perhaps use an Autoload script as a pure map data container then use a Node-inherited script to handle the editing and rendering functions?

Given what I know of Godot, I know either or both of those ideas are possible, but I feel I'm missing something fundamental.

Any suggestions?

EDIT: I'm sorry, let me clarify... I'm curious where and how to store the data during runtime, not how to store the data on disk. I wasn't sure if the best approach was to store the data using a Singleton (autoload script) and manipulate it with a node derived class or if there was a better structure as my intent is on the fly editing.

Also... While it may seem like reinventing the wheel, I'm planning on making the level editor a first class feature of the game, so I don't want to use the Build editor, or other tools like Slade.