Hide it by listing 'Preboot' (string) in config.plist/GUI/Hide (array)
But what are they exactly?
My intuition and a search tells me a) Recovery is ... well for recovery purposes in case the main one crashes. b) VM is virtual something? c) Preboot is... before you boot? This is obviously incomplete and I would love clarification or to be pointed to some resources.
I also noticed that I only saw the VM and Preboot options in Clover boot menu after using APFS in Mojave. I only had Recovery and the main one when using HFS in High Sierra. Does that sound right?
Refer to the example plists in the guide:
Look at GUI/Hide section.