It has been moved to some setting in an XML file - you should be able to find posts related to that.
I’ll try some search now too, lets see who gets it first (:
edit: nvm, I now see you are on Mac.
edit2: I tried editing grasshopper_kernel.xml according Request > space bar in GH but that didn’t work. If you are wondering where that file is you can go to $(USER)/.config/Grasshopper and open grasshopper.xml there
@DavidRutten, @curtisw - is radial menu supposed to still work?