>> Are you sure you don't want to split it into a new command that will simply
>> mark a set of files you expect here? E.g. all belonging to "registered"
>> statuses. That might require extra keypress, but vc-dir-root-registered is
>> probably not going to have the same short combination that vc-dir has
>> anyway. So it might be a wash, keypresses-wise.
>
> VC-Dir needs the same key prefix as is provided by Dired:
>
> * %             dired-mark-files-regexp
> * *             dired-mark-executables
> * /             dired-mark-directories
> * ?             dired-unmark-all-files
> * @             dired-mark-symlinks
> * s             dired-mark-subdir-files
>
> Then VC-Dir could provide, for example:
>
> * r             vc-dir-mark-registered
> * u             vc-dir-mark-unregistered
> ...

This is implemented as well: