Hi,
I recently found out that you can’t add time to your opponent on OGS. I think this feature should be implemented, I often don’t want to win by time but continue playing. This feature is useful for teaching games and ranked games alike.
What do you guys think? 
It’s come up before, currently the way to achieve this is to pause the clock. You can still make moves when the clock is paused, so it can do in a pinch.
We may very well implement explicit adding of time in the future, but it’s a little tricky depending on the time control system being used, both from an interface perspective and on the backend, and since pause meets the goal of wanting to extend the game past the initial agreed upon parameters, we haven’t made it a priority.