Although this is a feature request, it is for an existing plugin so I landed here.
It could be nice to have the option to toggle edit and preview mode within Outline plugin.
You could bring the pane away from the side area into the center pane region and quickly blockout an outline.
No need to add hashtags because everything is a heading.
Indentation would automatically adjust the heading level, aligning with the tree functionality that already exists.
Perhaps when pinned, each time you clicked a heading while in preview mode, it would inset the panes recursively within each other based on the heading hierarchy.
Along with this there could be hot keys to fold the panes which would keep a remaining tab like functionality in panes.
I kind of would like to go on, but know that you become radioactive here if you’re not atomic.
Just remembered I had a similar request before, so I am linking here: Indent driven auto heading creation mode