The plain_key group includes most of the keys you'd typically find on a keyboard: letters, numbers, arrow keys, backspace, and so on. Their names all start with key_ (like key_a).

Modifiers like ctrl and shift, however, are in a separate group - they're called plain_modifiers, and their names start with mod_ (like mod_shift).

plain_keys can be modified by any plain_modifier. This means that if you press the chords for key_a and mod_shift at the same time, the keyboard will recognize them both and send capital A.

You should never need to change the sequences for plain_key mappings. They're already defined in settings.yaml, in terms of the all-caps key names used internally by the keyboard firmware (like KEY_A).

You can edit the chords in a .kmap file if you want to re-arrange a mode's layout or create a new mode. Note that if the mode uses words, changing plain_key chords will also affect the chords for word mappings. See the word section for more details.