I would like to assign a custom menu to spacebar and RMB. The current menu assignments are somewhat meh. Is this possible?
What’s wrong with the menus that pop-up now?
Each item in the menu is already hotkeyed or easily accessed otherwise. If I can assign a deformations, polygroup, geometry menu instead, I feel it will speed up my workflow.
The shelves and trays are pretty much there for those functions. You can add/edit some hot keys. Learning the UI and playing the game as it’s dealt is advisable. Lots to see in Preferences. Changes made need to be saved as they aren’t automatically saved for you, Shift+Ctrl+I. Lots of helpful info on the Forums and in the link to the documentation below my post. Good luck.
Yeah I have created custom pallets and sub pallets, I would just like to hotkey those to the space/right click or customize the current menus associated with the current ones. I am quite adept at Zbrush, but I have been unable to find a workable solution.
Yes you can ( at least for RMB ) !
Disable : Preferences > Interface > Enable Right Click Popup
Then, if you have a wacom, go to your wacom driver settings and reassign your stylus button assigned to the right click and assign it to a unused keyboard key so you have it assigned to a custom palette you’ve made. If you’re using a mouse there are freewares like uberOptions ( for Logitech mouses ) that can do the trick. This way you’ve also got the 3rd button 
Et voila 
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For Space Bar I really don’t know, as when you work with a stencil it is used to pop the coin controller. You can assign something to it but the quick menu still appear.
( PS: I’m quite new here but I think this post is in the wrong section, personally I don’t mind but maybe you could move it if I’m right )