How to setup MAX transit to use WAN wire or LTE if cable connection is unavaliable

We are trying out a set of MAX transit duo. We have the VPN link up and running - the “server side” using WAN wire and the “remote side” using LTE. What we would like is - to have an option on the “server side” to use LTE if the WAN cable isn’t available, but how do I set this up?

Can you add some screenshots?
Normally on one side you just have multiple wans set on the speed fusion VPN connection.
Priority 2 Cellular , Priority 1 wan