[CentOS] Outliner plugin for editor

I am currently running not only Geany (on CentOS and on Windows) but also Gedit on CentOS, much of the use is as markdown-editors being a recent convert to this language. I would, however, also like to be able to essentially use it as an outliner - remember the old DOS outliners that were great for creating document outlines?

It would have been perfect had I been able to fold and unfold sections of whatever markdown document I am working on in Geany or Gedit but sadly that does not seem possible... Nor have I been able to find a plugin for Gedit or Geany that would add that functionality.

I do not want to have to use LibreOffice or something similar, it's too heavy and cumbersome.

Hoping that someone can steer me to a solution!Thank you.