How did you manage training non-tech people to edit yaml and markdown files?

How did this solve the CMS not supporting something they needed?

Did it simply make customizing functionality easier, since you are in total control of the codebase?

I got them to install MacDown, which is a standalone Markdown editor with side by side editing (text on the left, render on the right), and print a cheat sheet for links and images. Markdown is very easy to write. Nowadays there's probably an opensource wysiwyg editor.

The yaml part was very simple, it was handling the links for the menu entries..

Yes the customers wanted customized functionalities, like different ways to access the same pages, in the same tree.

Like you have Menu Item 1 => SubMenu Item 2 => List Item 3 is the same as Menu Item 3 => SubMenu Item 1 => List Item 5. Very few CMS do this, as the usual is to have a non cyclic tree hierarchy.

Here I had a main hierarchy reflected in the folder structure, and then they could add some links to the menu tree with the yaml files.

The whole thing was very simple. It took me about 16 hours to set up the whole site.