STARTT Upgraded Carriage - Easier to Print!

I really liked the STARTT alternate extruder mount from BogdanTheGeek. It improves the print stability, and cooling so much!

Unfortunately, I found it challenging to get the print to pause part-way through so I could insert the M3 nut into the body. I designed this remix so you can insert the nut after the print is complete (it just fits in with pressure).