Show desktop grid not working anymore (Ubuntu 20.04 KDE Plasma)
Most probable reasons:
- Disabled compositing - Shift+Alt+F12 (if shortcut not working, you should find this option in System Settings -> Display and monitor -> Compositor. Shortcut may be disabled by system, more in @svenevs )
- Disabled Desktop Grid (I learnt it hard way, that it's something different than Dekstop Cube and have different shortcut - that was answer to my problem). This option is in System Settings -> Workspace -> Workspace Behavior -> Window Management -> Desktop Grid