kmk_firmware/docs/en/sticky_mod.md

Sticky Mod

This module allows to hold a modifier while a key is being tapped repeatedly; the modifier will be released when any other key is pressed or released. This is for example useful if you want to switch between open windows with ALT+TAB or CMD+TAB, using only a single key.

Enabling the module

from kmk.modules.sticky_mod import StickyMod
sticky_mod = StickyMod()
keyboard.modules.append(sticky_mod)
keyboard.keymap = [
    [
        KC.SM(kc=KC.TAB, mod=KC.LALT),
        KC.SM(KC.TAB, KC.LSFT(KC.LALT)),
    ],
]

Keycodes

Key	Description
KC.SM(KC.key, KC.mod)	sticky mod