This is a tool holder that I created to try to learn how to use Fusion 360. My initial plan was to try and modify an existing tool holder design for the AnyCubic Mega but I could never successfully get through the BRep process. I gave up and started from scratch since it was a needed opportunity to learn the design functionality of Fusion.
There are two components, the main tool holder and the vertical mount plate. The vertical mount plate is attached using the single screw on the side of the CR-10 base just forward of the Z upright. There is a blind hole in the back to clear the other nearby screw on the side of the base. I used a couple #6 machine screws/nuts to attach the tool holder to the mounting plate.

update: I have revised, tested, and replaced the mounting plate files. The blind hole on the back of the mount plate was off by about 1/8". When exporting the F3D and STL files, I must have accidentally used an older backup than the final one which I had printed and used on mine. I took a pic of the revised version after printing the first couple layers to show hole alignment with the machine screws.