Summary

I needed to run some long running tests at work, but they do not allow unauthorised software to be installed, so no MouseJiggler. But there was nothing stopping me plugging in another mouse ;)
I got the smallest board that allows for HID I could find. There are probably smaller around. Flashed some code and designed a case.

The board is the Waveshare RP2040-One, available here: https://thepihut.com/products/waveshare-rp2040-one

I used C as I normally work with ESP32 and Arduino boards, as the code is very light, I have uploaded it here (mousejiggler.ino)

As it moves the mouse cursor only 1 pixel in one direction and then 1 pixel back in 10 milliseconds, you cannot even see it move and it doesn't interfere if you are working away and forget to remove it.