SUMMARY
KDE in general seems to accept key sequences (as one finds in emacs) as valid keyboard overrides. e.g., you can set "Open" to be C-x C-f.   However kwin does it, it only allows you to set single keys. Since the emacs command to close a window is C-x 5 0, that makes it impossible to set that sequence.


STEPS TO REPRODUCE
1. go into settings., shortcuts find a key to override in the Kwin section (e.g. Close Window)
2.  Observe you can't set window functions to sequences of keys

OBSERVED RESULT
can't set key sequence

EXPECTED RESULT
Be able to set key sequence like you can in other parts of KDE.

SOFTWARE/OS VERSIONS
Windows: 
macOS: 
Linux/KDE Plasma: kwin 5.27.8
(available in About System)
KDE Plasma Version: 
KDE Frameworks Version: 
Qt Version: 

ADDITIONAL INFORMATION