Created attachment 134526 [details]
Image of the Mouse Mark Setting Dialog box, showing their is no Shortcut action to change.

SUMMARY
You have hard coded the Shft+Meta.

There is no Shortcut Key setting to change the default Shft+Meta? It's not in System Settings | Shortcuts either. Reason for my use is, using OBS Studio I capture a VM where I need to draw on the screen, but when I change change back to the main desktop, I need to draw there also. So I need to be able to change the VM/Main Desktop to another Shortcut Key. 

STEPS TO REPRODUCE
This feature is KDE's Workspace Behavior | Desktop Effects | Mouse Mark.

Below the Settings it says. "Draw with the mouse by holding Shift+Meta keys and moving the mouse"

OBSERVED RESULT
Can't change, I assuming it's hard coded.

EXPECTED RESULT
Just like the other Shortcuts Keys, I should be able to change this.

SOFTWARE/OS VERSIONS
Operating System: openSUSE Tumbleweed 20210101
KDE Plasma Version: 5.20.4
KDE Frameworks Version: 5.77.0
Qt Version: 5.15.2
Kernel Version: 5.10.3-1-default
OS Type: 64-bit

Processors: 8 × Intel® Core™ i7-9700 CPU @ 3.00GHz
Memory: 125.7 GiB of RAM
Graphics Processor: GeForce GTX 1660/PCIe/SSE2

ADDITIONAL INFORMATION
I see this was reported for version 5.13.4:

Bug 337043 - Mouse Mark has no user-definable shortcut, hard-coded one interferes with others 

Reported: 	2014-07-04 12:57 UTC by DrSlony
Modified: 	2018-09-27 18:10 UTC

....Will this be corrected soon or in the next version?  I need this feature.