Custom mechanical keyboard firmware like QMK [1] and ZMK [2] support custom chords called "combos". Basically if the combo's set of keys is hit (within some timeout which defaults to 50 ms) then a specific keycode is sent. You then get a fun game of identifying low probability combos and mapping then to useful keycodes. You also start realizing there's some prime real estate to take advantage of. Two-key combos require some thought cause bigrams can be surprisingly common. Three-key combos are basically open though.

In migrating from the ZSA Voyager to a 36-key keyboard (Chocofi) I've relied on combos as I don't like overloading keys with tap-versus-hold behavior as I can never get the timing down. For example my left index, middle, and ring finger mashed down on the home row (resting position) is escape in my current layout (Colemak mod DK which means keys R, S, and T). It's three fingers but hardly any extra effort. I've managed to do away with a symbol layer and have been quite happy with the result. If anyone is curious here is my "36-key training layout" for the ZSA Voyager [3] and my current Chocofi layout [4].

1: https://docs.qmk.fm/features/combo

2: https://zmk.dev/docs/keymaps/combos

3: https://configure.zsa.io/voyager/layouts/d7L0v/latest/0

4: https://github.com/vietjtnguyen/zmk-chocofi/blob/main/config...