When exporting a keymap, the current keymap should be preselected

[rillig]

After having switched to a new keymap, I want to print it, for reference.
When I try to do that, I get a dialog where I can select the keymap to print.
The preselected item seems to be the platform's default keymap (GNOME in my case).
Instead, the preselected item should be the currently active keymap.