I have Shelly switches connected to a Hubitat however I would like to add a wall controller so I can control them from a centralised location without the need for the app.
What are the options
And
Can I use the Shelly wall controller. Pair them to that via home WiFi AND the Hubitat wireless connection simultaneously
Assuming you have z-wave dimmer/switches controlling your lights (you did not specify the protocol of your shelly switches and they have up to four flavors).
I like the heatit Z-Push wall controllers (Controllers - Heatit). Not cheap but being z-wave 800 the battery goes well over a year and you can configure then with 1 to 3 switches. I use the Generic Z-Wave Plus Button Controller as device driver and you can create a direct association with the lights you want to control. This greatly improves the responses for dimming actions and will allow you to control the lights even if the hub is down.
For solid response times I would not go the Wifi route, but that is just my opinion.
Get a wall plate one gang larger than it had. Screw the Zooz magnetic plate into the wall plate then put it back up on the wall, The image shows the Zooz maganetic holder on what is actually a two gang box. It hangs over but looks normal. (Tip, you may need to trim off two turns of threads from the plate screws. There is a provision for that built into some wire cutter tools.