Theme editor anywhere?

In the last weeks I tested out some smaller CMS. Grav seems to be one of the best choices. However, I am missing one very important thing: a kind of theme editor (e.g. see in the Bolt CMS admin area, where themes are grouped in folders by name and then you can open a theme and open/edit single parts of a theme. See here:

In Grav you can only click on a theme and do some basic configuration. The Gantry themes offer some more configuration, okay. I can use the Edit plug-in, but it does not offer the visibility I would like (= grouping all files and file types – css, twig etc. – of a theme in one view). An alternative would be an “Expert” view of a theme where to edit all the files.

Did I oversee something or is there any workaround/plug-in for this?