SUMMARY
I have a keyboard with multimedia and some other keys. I wanted to assign them to launch applications such as VLC player and KCalc.
And I would also like to be able to launch other applications such as LibreOffice Writer or others with hot keys.

STEPS TO REPRODUCE
1. I open the System parameters, Hot keys, then click button Add application, select KCalc, then I click the Add custom shortcut button. I click the button Calculator on the keyboard, the inscription inside the button changes, then I click Apply.

2. In another case, I do the same for the VLС player and the corresponding button on the keyboard.

3. And in another case, I do the same for LibreOffice Writer and the keyboard shortcut Meta+W.

OBSERVED RESULT
Nothing happens, hot keys in all cases do not start the application.

EXPECTED RESULT
Hotkeys must launch their applications ...

SOFTWARE/OS VERSIONS
Windows: 
macOS: 
Linux/KDE Plasma: OpenSUSE Tumbleweed/5.19.0
(available in About System)
KDE Plasma Version: 5.19.0
KDE Frameworks Version: 5.70.0
Qt Version: 5.15.0

ADDITIONAL INFORMATION