Some other third-party editors with code folding include Atom, VSCode, TextMate, et cetera.
Many have simple packages or bundles for running the sketch from the editor:
There are things you might miss from PDE, like reference tooltips, the “stop” button, tweak mode, an app export wizard, etc… but you can always switch back into it to use those things. Just be careful of having the same sketch open in both, as PDE can sometimes be aggressive about autosaving.