topdown RPG, camera must move only when character hits the edge.

Lots of ways to do this, but it is going to depend on how you've structured your game - that is, pick one

For this game, each section had its own scene with an area that fired a signal when the player entered/exited the boundary, which enables the camera in that room. But that's essentially putting lots of scenes together to form a map (there's no need to have all the scenes loaded, but that's a different thing). It looked like this in the editor with all the scenes enabled:

Another could be just to move the camera X/Y +/- its height/width when the player leaves the visible area (e.g. +/- a width/height, hitting a boundary trigger, visibility notifier...), or just to never move it at all and move the world instead. I also wonder if you could adjust the drag_* properties of the camera and its configuration so it moves the screen dimensions when necessary? No code at all, just camera configuration.

you could use camera boundaries

grimm_ So like in the old NES Zelda? Do you also want to scroll over to the next room or simply swap it?

I remember there being a HeartBeast tutorial recently about doing something like this.

grimm_ it wouldn’t be complicated if each level was a different scene, but it may take some coding and trial and error to do a map like that

grimm_ I was trying to make only one "map", but my knowledge level is quite poor. so I'm doing this way, tho.

May I ask why you want to have only one scene instead of going the probably easier route of making each screen its own scene? It seems like you are trying to make your life harder than it needs to be.

grimm_ Ah, sure. In that case don't worry about it and experiment. Making mistakes and getting into problems is the best way to learn because it means you are pushing your boundaries. But don't worry about performance as long as you are still a beginner.

grimm_ you could always back your project up in a private github repo so you can always revert back if something breaks

TheMidnightWolf For that you don't even need to push your code anywhere else. Just create a local repository and commit your changes. Now you can always go back to previous versions.