I would like to, when in a conversation, go back to chat list within a single (fullscreen) gesture. I propose swiping from left to right, as in Telegram.
You need to use arrow/button/back-gesture (those lucky Android 9+ users) instead
As you said, Android already has built-in “back” function, which you can bind to a gesture.
Wouldn’t it be confusing if you look for swipe-to-reply, and instead go back?
that depends on the trigger (swiping from an empty space or selecting a message), I suppose…
i think, for such actions, it is better to use what the os provides. maybe a hardware button, maybe a software-button, maybe a gesture. we just don’t care, and only listen to the event “user wants to go back”.
one otherwise easily enters areas hard to maintain, eg. android 10 will support swipe-to-go-back by the system - apps that use this gesture on their own would probably need adaption.
of course, this is only a rule of thumb, however, it often turns out in the past, after all experiences, that this is a good way to go, esp. on android, where you have tons of different manufactors with different android flavours.
maybe it is just me, but in Telegram I constantly go back to chat list when I actually want to reply a message, I just don’t get used to it, maybe because I am used to other apps that have the reply gesture in the direction telegram uses to go back, it is quite annoying, I find this gesture totally unnecessary, when holding the phone with one hand I prefer to press the back button/gesture of the phone, but well just MHO 
Ok, WA do that, but Telegram include both gestures (go-back in one direction and reply in the other one), it’s possible to do such thing, that’s what I’m saying
If I am not mistaken, the general go-back functionality can be configured with an Android setting, but it could be accessible in newer Android versions only.
yes, but what I’m asking is for a full-screen gesture, one that doesn’t involve edges. In my case, Android gesture to go back is swipe from any border (not too low, not too high) to the opposite one, and I would like to be able to go back e.g. starting the gesture on the center of the screen.