Technically you can use an editor for almost everything. I've been using vim to edit my projects after setting up the base project in the godot IDE. The trick is, not to use scenes. I've got the one scene that was set up when I created the project. Everything else is generated in gdscript as classes.
There are drawbacks to this. You can't use a lot of godot's neat features without the IDE, and scenes load faster. If you're using a standard editor, like notepad, you'll probably adapt to godot's editor quickly. If you're used to a stateful editor, like vi, you might want to continue using it.
