Couldn’t find an appropriate topic. I’ve played a couple of correspondence games. I was losing and we were in the end game. In one what I was going to was pretty obvious. Within one nanosecond my opponent played his stone. He wasn’t on line, so far as I could tell. In another, again end game and again I was losing, I had perhaps three moves I could make (none making difference to the outcome) but again within a nanosecond my opponent responded and again he wasn’t on-line. Can you pre-program your moves?
Yes. There is a button on the right side of the game called “plan conditional moves” I think it’s enabled, when analyzing the game is also allowed
What @Senffarbe says. Right sidebar/flyout menu, see screenshot.