Na minha máquina, parece que o gedit mantém seus temas recém-adicionados em:
~/.gnome2/gedit/styles/
embora eu acredite em algumas instalações, é em:
$HOME/.local/share/gedit/styles/
Os temas originais são (na minha máquina) em:
/usr/share/gtksourceview-2.0/styles/
Portanto, as informações abaixo não são particularmente relevantes, embora eu deixe que isso continue, porque pode ajudar de alguma forma.
Da documentação em: link
To install a style just place its XML file into a folder of the style search path.
GtkSourceView 2
A typical search path for GtkSourceView version 2 looks like:
~/.local/share/gtksourceview-2.0/styles/
/usr/share/gnome/gtksourceview-2.0/styles/
/usr/local/share/gtksourceview-2.0/styles/
/usr/share/gtksourceview-2.0/styles/If this does not work in your distribution you can find out your style search path with this python script. To run it you need the python bindings for GtkSourceView 2. In Debian-based distributions this is package python-gtksourceview2.
GtkSourceView 3
A typical search path for GtkSourceView version 3 looks like
~/.local/share/gtksourceview-3.0/styles/
/usr/share/gnome/gtksourceview-3.0/styles/
/usr/local/share/gtksourceview-3.0/styles/
/usr/share/gtksourceview-3.0/styles/