The Desktop Grid effect needs the option to set what a specific mouse button does when clicking on a window or desktop.
Or it could use the options of the Present Windows effect.

I don't use the put-window-on-all-desktops action very often, yet this is triggered by both, the right and the middle buttons.
The Present Windows and Desktop Grid effects are very similar, so the user expects them to behave the same way. I sometimes forget which effect uses which mappings when doing things quickly.

Reproducible: Always