I have a pluggable thunderbolt 3 dock at my desk and wanted a better mounting situation. I traced the profile of the dock and made an SVG, loaded it into TinkerCad and came out with this. 

I don't have a thunderbolt 4 dock to test with, but it would appear to have the same shape, so this should work with it. 

I'm super happy with it! I used some half inch lath screws to secure it to my desk and it feels solid.

You'll need to print two with one mirrored over any axis. I had trouble with the cutout around the tab, and ended up printing perimeters on the first layer all the way down at 3mm/s. 

Mounting tips: I mounted one end bracket, put the dock in the mounted end bracket, put the screws in the other end bracket and put it on the end of the dock, and then pressed to mark screw locations. It's pretty close but they could've been slightly closer together. Maybe a future addition could include an interlocking spacer that sticks out?