Problem: 

Cheap diode laser don't have a Z axis motor, the gCode neede for them also usually don't have Z axis values. So how can I lift the pen when needed? For most problems, somebody already came up with a solution, though...

Solution (Software):

After some research (5 min of googleing) I found that thread on reddit:

https://www.reddit.com/r/PlotterArt/comments/1faix70/comment/n3kuu1u/?context=3

Where somebody already did something in CircuitPython on a RasPi Pico:

https://shibumee.com/harry_plotter/

So I did some tests with a XIAO RP2040 and it looked great.

Solution (Pen holder):

The harry plotter needs a lot of 3D printed parts, also for the pen holder. While doomscrolling on AliExpress I found a complete pen holder assembly with for way less than my nerves would have costed in the same time. So I just ordered that.

Solution (Electronics):

I wanted to make a small PCB though, which allows for switching between laser and plotter using a relay. I should be small so I went for a XIAO RP2040 instead of the Pico. (see files)