Ok, so you are building your own engine, that makes a lot more sense, and you do realize that... the editor itself is actually quite substantial a task, to get everything coherent and also functional.
Honestly, best of luck to you!
No clue if you've seen these before, but maybe they could be helpful?
https://david-delassus.medium.com/trying-out-sdl3-by-writing-a-c-game-engine-c9bb13156b74
https://github.com/linkdd/sdl-game-engine
https://blog.conan.io/2023/07/20/introduction-to-game-dev-with-sdl2.html