Earlier quoted context omitted.
But with 2-3 fingers you already have lots of combinations. 2 thumbs are enough. I have been toying with some ideas for a game and thought about the potential for normal use cases. Intuitive (like swiping and pinching) is none of it though and it can only be useful once muscle memory kicks in. So I guess this is the reason, we do not have a global standard for anything advanced multitouch.
Given 2 finger pinch-spread is already taken for zoomout-zoomin, what are the remaining useful combinations for 3 fingers? It can't detect which finger you're using. It should support one-handed operation, so the 3 finger gesture should be possible with one hand. You'll likely have to use middle and ring fingers, which are mechanically connected, so relative motion would be difficult. I think you're wrong. There are…
Well, people who played the violin or alike can do this, but yeah, it was hard work to learn and cannot be expected of the general user.
So yes, it cannot be anything complicated.
One of my ideas is to use the position of the fingers and the timing they touch. No matter which finger, what matters is the position they touch down relative to each other. So 2 (or 3) touches, like double click, but with 2 fingers and you evaluate the positions.
Simple variant: "pointing finger", "middle finger" -> one action (one touching point, then another touching point shortly afterwards left of the first touching point)
"middle finger", "pointing finger" -> another action (first touching point, then the other touching point to the left of the first one)
Or you can use the 2 thumbs, or thumb and pointing finger. And use up and down as well. So you have "middle" "up"; "middle" "down"; ...
And the actions could be anything, like "middle" "left" could select the next word to the left or go to the beginning of the line.
But my main thinking evolved around game actions, but it is the same principle.
And then you could also advance it with "middle" "left" "middle", the only limit are the coordination skills of your average user.
And ... the hardware limits. I have never really implemented those ideas, because I got frustrated very quickly(some years ago) with how the native touch handling of the OS got in the way, and some unprecise sensor input. But if you keep it simple, it should be doable. I guess I am now motivated to give this experimentation another shot real soon ..