Increase list under "Open Recent"

[David Hurka]

> 3. I do not see any options for kreadconfig5 to dump existing groups
> nor existing keys.
> It seems to require that you know exactly what groups and keys exist in
> advance.
> Am I missing something?

The settings are stored in ~/.config/okularrc or similar.
In that file search for [Recent Files].

It looks like there is no key that controls the count, instead the application 
is responsible for chosing a sensible value. See setMaxCount() method:

https://api.kde.org/frameworks/kconfigwidgets/html/classKRecentFilesAction.html#a9f41c649046f251ec8d4020aaa3ba3e5