Action for Mouse "Grab"

Could you add support for a "grab" action? A press-and-hold gesture could initiate the grab, keep it active while held, and release it when the gesture ends.

This would work well with the MX Master 3's capacitive side button, allowing me to grab and manipulate objects while the button is pressed.

there is no such thing as a grab on macOS. There might be something like it in some specific applications. Where are you trying to use this?