The dichroic mirror arrived, I printed a mounting bracket for it and put everything back in the cash case.

I secured the mirrow with a piece of tape on the top against vibration from the laser fan. The parts inside the case are just placed on a layer of double sided tape, but if you want you could also secure the parts with magnets or align them and mount them with screws. The Red Dot Laser can be turned on by sending M8 and turned off by sending M9 to grbl.

I also added a switch to turn the blue laser power on and off to prevent the laser from shooting at max power while powering up the controller. This behavior leaded to a small damage on one of the mirrors as the laser hit the mirror on the edge while powering the controller on, so it will be the best to prevent it from happening again.

This switch could also be replaced with a key switch to add a safety feature.

With the red dot laser working and the machine working reliable I can write the complete instructions for building one.

In fact this is my first project until now which I could call completed, because everything I had in mind for it worked out :)