If I leave a Facebook group, does a notification appear in the group? (I'd like to leave a group, but don't want the other members to know)
No.
No one is notified when a user leaves a group in Facebook. Not even the admin.
They will know only if someone looks to make sure you are still there.
Everyone in the group is notified. There is a notification saying what member left. I know this because I belong to a group and have left many times..as soon as I do, I receive a call from one of the members asking why, and because when someone else leaves, I can see the notification.
Although no one will be notified if you leave a public group, everyone in a (private) Message thread will see a line in the thread if you choose to leave it.
Actually everyone in the group is notified when a member leaves. It days. "So and so left the group".