SOLVED How to add dynamic mirrors to your modification?

The basics are explained here: https://documentation.beamng.com/modding/vehicle/sections/mirrors/
Basically, you need a mesh with a material called "mirror". The geometry of it will decide if it's a flat or convex mirror (keep in mind that the material has a normal map, so a mirror that is 100% flat model-wise will still be a bit convex, this will hopefully be changed in future updates). Then you need 3 nodes on the mirror Jbeam structure, which are aligned with the model, to act as the initial position and rotation setup for the camera that will record what is displayed in the mirror. Then you tweak the camera position and rotation from the initial values using refBaseTranslation and baseRotationGlobal modifiers, until it's in the middle of the mirror. The units are meters and degrees. You can show the camera position in Vehicle Editor (Shift+F11), by adding the mirror debug app. You can also use the offsetRotationGlobal modifier to tweak the rotation of the mirror view, but it's better to tweak the model rotation instead.