The boost gauge is controlled by the encounter bar in edit mode.
Unless you’re talking about the vehicle action bar itself, you can use /fstack to find the name of the frame and use the Frame:Hide() or Frame:Show() commands (where Frame would be the name of the frame) to toggle. Coincidentally, hiding the vehicle bar allows you to access edit mode.
/run OverrideActionBar:Hide()
/run OverrideActionBar:Show()
You could do the same thing with the boost gauge.
/run PlayerPowerBarAlt:Hide()
/run PlayerPowerBarAlt:Show()
Note that these will only last until you reload your ui.