kmk_firmware/docs/modholdandtap.md

ModHoldAndTap

This module allows to immitate the behaviour of ATL+TAB or CMD+TAB, etc.
Basically, it will hold the mod and tap a key on a layer other than default layer. The mod will be released when any other key is pressed or the layer key is released. The key will do nothing when it is placed on the default layer

Enabling the module

from kmk.module.modholdandtap import ModHoldAndTap
modholdandtap = ModHoldAndTap()
keyboard.modules.append(modholdandtap)
keyboard.keymap = [
    [
        KC.MHAT(kc=KC.TAB, mod=KC.LALT),
        KC.MHAT(KC.TAB, KC.LSFT(KC.LALT)),
    ],
]

Keycodes

Key	Description
KC.MHAT(KC.key, KC.mod)	holds the mod and taps the key