My first model, made in FreeCAD.

The letters are embedded 0.5mm into the top surface, setup as Modifiers in Bambu.3mf for easy customization.

I printed at .08mm High Quality and was happy with the result.

Use 3x1mm round magnets press-fit into the bottom face. The magnets stick to a metal plate on the face of the button itself, so polarity should not matter when attaching magnets.

The print is usable without supports but I printed with supports and used the Gray PETG as support interface to make cleanup easier, fit better.