On Desktop, you can move Notebooks under other Notebooks making subdirectories. There appears to be no way to do this on mobile though.
Right now attempting to drag Notebooks results in a long hold bringing up a menu to rename the Notebook
Maybe a long hold would bring the menu which allowed renaming, and moving of notebooks. Or at least an option in the settings menu go into some sort of “edit mode” allowing for the moving of Notebooks.
There was a PR open for it a while back. The OP did not implement the requested changes and later abandoned it, thus it got never merged.
I'm surprised the OP would't be willing to do such a simple yet crucial change himself, but oh well 
I don't think you understand what OP means. OP is the original poster. The person who created a post, PR, issue.
I can re-open the PR and you can do this simple yet crucial change yourself. 
That makes a little more sense, thanks for the clarification, I meant Laurent adding the feature. As to re-opening it, I might decide to someday but at the moment I don’t know quite enough about react and electron to do that yet, still in the process of learning.