pert:
The problem is you're using Cosa which, unlike Arduino AVR Boards, doesn't include an HID library. Is it necessary for you to use Cosa? If not then just choose Tools > Board > Arduino/Genuino Micro and the problem will go away. If it is necessary for you to use Cosa then I can think of a couple possible solutions but haven't tried any because I don't use Cosa:

First possible solution:
Delete the line:

from your sketch. Cosa may be based on the older versions of the Arduino IDE, which had the Mouse functions built into the core and thus did not require this to access the Mouse functions.

Second possible solution:
Copy the HID library from the libraries folder of the Arduino AVR Boards package to the libraries folder of the Cosa package.

It's looking good. It uploaded, but I need to assemble and test to be sure. Thank you so much for your help!