This will send "john.doe@example.com" if you chord E and M together, and clear the current line with Backspace and Left-Shift. You could change this to do stuff like play sounds or change settings.
It is worth noting that `COMBO_ACTION`s are not needed anymore. As of [PR#8591](https://github.com/qmk/qmk_firmware/pull/8591/), it is possible to run your own custom keycodes from combos. Just define the custom keycode, program its functionality in `process_record_user`, and define a combo with `COMBO(<key_array>, <your_custom_keycode>)`.
It is worth noting that `COMBO_ACTION`s are not needed anymore. As of [PR#8591](https://github.com/qmk/qmk_firmware/pull/8591/), it is possible to run your own custom keycodes from combos. Just define the custom keycode, program its functionality in `process_record_user`, and define a combo with `COMBO(<key_array>, <your_custom_keycode>)`. See the first example in [Macros](feature_macros.md).
## Keycodes
You can enable, disable and toggle the Combo feature on the fly. This is useful if you need to disable them temporarily, such as for a game. The following keycodes are available for use in your `keymap.c`