I haven't seen the QMK firmware, but there are multiple ways to accomplish it. Here are a few that I can think of: A popular technique is to use tapping term,

I haven't seen the QMK firmware, but there are multiple ways to accomplish it. Here are a few that I can think of: A popular technique is to use tapping term, which is where tapping one of those buttons two, three, four, etc. times in quick succession will trigger something different like a dash or slash. Some keymaps are configured to send regular characters when buttons are quickly pressed and activate "layers" when buttons are pressed and held. A layer would contain the dashes and slashes. Another layer would have numbers. Other layers for modifiers like F1, F2, F3, etc. Alternatively, one-shot layers are a type of layer activation where one tap activates a layer and the next tap activates the desired dash/slash/etc. character. I would prefer this method for this type of device because it likely requires less taps than the tapping term method and doesn't require fingers to hold down buttons like the previous one mentioned. It also pairs well with one-shot mods, which is the same concept, but for shift, control, alt, the windows key, etc.