This was discussed a couple of years ago (2020…2021) in two or three different threads until we finally got a solution… See here
In V8 I do this: go to “Rhino settings → Mouse → Middle mouse button” set “Popup this Toolbar” to “Popup” - and in “Rhino settings → Advanced” set Rhino.Options.Advanced.LeaveFloatingPanelsHiddenOnMac to true