kmk_firmware/docs/en/mouse_keys.md

Mouse keys

To enable mouse cursor and/or mouse buttons control from the keyboard add this module to list:

from kmk.modules.mouse_keys import MouseKeys
keyboard.modules.append(MouseKeys())

Keycodes

Keycode	Description
KC.MB_LMB	Left mouse button
KC.MB_RMB	Right mouse button
KC.MB_MMB	Middle mouse button
KC.MW_UP	Mouse wheel up
KC.MW_DOWN, KC.MW_DN	Mouse wheel down
KC.MS_UP	Move mouse cursor up
KC.MS_DOWN, KC.MS_DN	Move mouse cursor down
KC.MS_LEFT, KC.MS_LT	Move mouse cursor left
KC.MS_RIGHT, KC.MS_RT	Move mouse cursor right