A CAD navigation tool is a great help for the construction and three-dimensional orientation in a technical drawing. A colleague of mine once said that it later feels like a body part has been amputated when you have to design without SpaceMouse after you have gotten used to it.
I use the SpaceMouse from 3Dconnexion for business and private use. This is very good in handling and function. Unfortunately, only two freely programmable buttons are installed here and the price for this simplest model is very high at 129 €. For me, the freely programmable keys are a must so that I don’t have to constantly switch between the keyboard and the SpaceMouse with my left hand. The 3Dconnexion SpaceMouse Pro offers these additional functions, but at 299 € it is absurdly expensive. I didn’t want to support that and thought about something of my own.

My 9 Keys Extension

There are nice kits and instructions to build a freely programmable keyboard from an Arduino Nano. As an alternative, I found a 9-key keyboard on Amazon where each individual key can be freely assigned and even written with macro functions. This ready-made and very compact keyboard was cheaper at 29 € than only the components for the do-it-yourself variant.

I have constructed a simple holder for keyboard and SpaceMouse with a palm rest that is comfortable for me. The keyboard is slightly offset from the SpaceMouse so that I can reach the keys quickly and comfortably. Cable outlets are provided for the mouse and keyboard. Finding the right drivers for the keyboard was the most difficult part of the whole project. Here is the download link vor Version 1.5: https://github.com/showjean/ps2avrU/releases
I have been using this setup for several months now and am very satisfied.