I think you and I are at the same point in Godot progress. I have chosen to do everything in one scene and leave the code where I first put it when experimenting. It's my project, I'll find the code when I need to change it. Lots of crazy overabstraction on YouTube tutorials by people who are not software engineers but who think obfuscating working code makes them so. Let's sadly look away from why our industry gives them the impression that that's a good idea. I will finally have to learn separate Scenes when I give up on one level with teleports and shift to loading, which may be never.

I watch clickbait Godot tutorials on YouTube on 2x speed in my spare time. When I stumble into a problem that I suspect has been solved before, like your resizeable platform problem, I go to YouTube and see if I can find a reference. For your case, I think you're looking to create a Tool, maybe. You'd need to define your platform as a programmaticly sized node using either tile maps or that texture thing that lets you define the corners, the fill texture, and size from there.

But if it were me I'd lift the code for the platform out of the node that sizes it. Then you can just hand edit each platform, and link the platform to the controlling node (or whatever relation you see fit to use).

It's important to focus on the game over the infinite ways you could structure code in an environment of such high flexibility. At least coding your game with bitmaps in C you can't get lost in trifles, you'll just spend more time reimplementing and understanding the basics. See raylib.