Re-bind keys previously bound to Action Bar 1 to the Vehicle Buttons when using the default UI, so the button on-click effects work properly.

This feature does require that the keys you want to control the vehicle buttons (usually 1-6) are actually bound to Bar 1. It will however still work if they are not, as long as you have the bar bound to those keys set as possess bar.

Bartender4.lua

@@ -174,6 +174,24 @@ function Bartender4:UpdateBlizzardVehicle()
 		RegisterStateDriver(MainMenuBar, "visibility", "hide")
 		RegisterStateDriver(ShapeshiftBarFrame, "visibility", "hide")
 		RegisterStateDriver(PossessBarFrame, "visibility", "hide")
+
+		if not self.vehicleController then
+			self.vehicleController = CreateFrame("Frame", nil, UIParent, "SecureHandlerStateTemplate")
+			self.vehicleController:SetAttribute("_onstate-vehicle", [[
+				if newstate == "vehicle" then
+					for i=1,6 do
+						local button, vbutton = ("ACTIONBUTTON%d"):format(i), ("VehicleMenuBarActionButton%d"):format(i)
+						for k=1,select('#', GetBindingKey(button)) do
+							local key = select(k, GetBindingKey(button))
+							self:SetBindingClick(true, key, vbutton)
+						end
+					end
+				else
+					self:ClearBindings()
+				end
+			]])
+		end
+		RegisterStateDriver(self.vehicleController, "vehicle", "[target=vehicle,exists,bonusbar:5]vehicle;novehicle")
 	else
 		MainMenuBarArtFrame:UnregisterEvent("UNIT_ENTERING_VEHICLE")
 		MainMenuBarArtFrame:UnregisterEvent("UNIT_ENTERED_VEHICLE")
@@ -188,6 +206,9 @@ function Bartender4:UpdateBlizzardVehicle()
 		UnregisterStateDriver(MainMenuBar, "visibility")
 		UnregisterStateDriver(ShapeshiftBarFrame, "visibility")
 		UnregisterStateDriver(PossessBarFrame, "visibility")
+		if self.vehicleController then
+			UnregisterStateDriver(self.vehicleController, "vehicle")
+		end
 	end
 end