Ability to create new theme files.

[Dickie]

It would be really nice to be able to create a new file with the theme editor (e.g. loop-category.php) or a new page template for example, when you realise that you need one.

This is related to the last comment in #12716 as creating new versions of parent theme files in your child theme also would be very useful.

Yes.... I know you can use FTP to do this, but when you want to create a new page template quickly and you are in the wrong place it would be a very useful feature.
By the same argument we have the theme editor in the first place, let make it even more useful.

FWIW, this has been suggested as part of a theme editor overhaul.