Hi Cote,
To find the meshes used with the OpenXR plugin: In your Content Browser panel click ‘Settings’ and enable “Show Engine Content” and “Show Plugin Content”. You’ll then be able to find the controller meshes in the Plugins/OpenXRContent folder.
It might be a good idea to copy these meshes+materials into your Content folder if you’re going to be making changes to them.
Looks like there is only one material on these meshes, so I think one path forward would be to create and control “texture masks” to dynamically highlight the buttons.
Another (easier?) idea is to have button-shaped meshes attached to the main controller mesh, and then show/hide them as needed.
Cool problem, excited to see what you come up with!