I'm just getting into making my own designs, so I just had the random thought of hanging various accessories from the arm of my chair ( for example my driving sim shift stick )
The actual STL is a new version from the one in the little demo video, just because I had to redesign the slot part, it was way too fragile.
If you have an IKEA Markus like me you could just print it, otherwise I guess you could resize/scale it to fit.
The author hasn't provided the model origin yet.