@eli OmniOutliner. Related, have you considered a mind mapping option? MindNode 5 is fabulous. I find outliners and mind mapping to be very closely related.
@jthingelstad Ooooh, I havn't yet explored mind mapping. I'll take a look!
@eli Omnioutliner is awesome if you want an awesome GUI app. I do almost everything in Spacemacs these days