I think ideally you should start with the editor and only move to code once you have a need the editor can't provide.
Think of Photoshop. You'd never want to code your own effects or workflows if they're already there. In the case of an game editor you'll eventually need to code some behaviours or interactions between entities, and even then you might be able to do those with a visual editor which a few engines come with.
In a way, code should almost be your last resource when making a game.
Also think that making a game is a heavily iterative process, you want to reduce the friction between iterations as much as possible. So even code should be targeted at exposing options that you can edit on the fly within the editor. The benefit of a good editor is that it is WYSIWYG. So if say, an object is not lining up, has the wrong colour, particle effects are staying for too long, etc you can quickly pause and adjust the values in the editor and see the result immediately, no need to be tweaking values in a file.
Think of Photoshop. You'd never want to code your own effects or workflows if they're already there. In the case of an game editor you'll eventually need to code some behaviours or interactions between entities, and even then you might be able to do those with a visual editor which a few engines come with.
In a way, code should almost be your last resource when making a game.
Also think that making a game is a heavily iterative process, you want to reduce the friction between iterations as much as possible. So even code should be targeted at exposing options that you can edit on the fly within the editor. The benefit of a good editor is that it is WYSIWYG. So if say, an object is not lining up, has the wrong colour, particle effects are staying for too long, etc you can quickly pause and adjust the values in the editor and see the result immediately, no need to be tweaking values in a file.