Bug 455530

SUMMARY
I noticed that after assigning Meta+Up to "Maximize Window" and clicking Yes on the conflict found dialog that new shortcut does nothing, but the original shortcut (Meta+PgUp) still works. However, if I were to turn off the default shortcut of the "Quick Tile Window To The Top" action (Meta+Up) first, and then assign Meta+Up to the "Maximize Window" option, then the shortcut works as expected.

STEPS TO REPRODUCE
0. Reset keyboard shortcuts to the defaults (initially in my case there was no default shortcut shown at all for the "Quick Tile Window To The Top" option)
1. Assign Meta+Up as a custom shortcut to the "Maximize Window" action of KWin
2. Click "Yes" on the "Conflict found" dialog box
3. Click "Apply"
3. Press Meta+Up

OBSERVED RESULT
Nothing happens.

EXPECTED RESULT
The current window should be maximised.

SOFTWARE/OS VERSIONS
Operating System: Arch Linux
KDE Plasma Version: 5.25.0
KDE Frameworks Version: 5.95.0
Qt Version: 5.15.4
Kernel Version: 5.18.3-arch1-1 (64-bit)
Graphics Platform: Wayland

ADDITIONAL INFORMATION
After the reassignment the checkbox for the default shortcut of the "Quick Tile Window To The Top" option does get unchecked.