[regression] screen grab, monitor selecting missing

Summary
Using multiple screens and I want to record one of them. I cannot select which screen to grab.

STEPS TO REPRODUCE

1. try to select which screen to grab

OBSERVED RESULT

The feature is absent

EXPECTED RESULT

We should be able to select one of multiple screens.

more detail see: https://bugs.kde.org/show_bug.cgi?id=407755