Download the latest maccarron and Make your main bar a possessed bar. Go through the bar options until you get to the possessed bit and then just add the buttons you need. I think 6 was enough for me during the zombie event. Im not sure how many skills you get on a mount bar.

I havent tested this btw, im just going off what other people have been saying elsewhere on the mod forum and how i got it to work during the zombie event for my 5 guys.