This one is pretty much what you would expect. You can remove a docker node from a swarm with the leave command. Here is an example of needing to use the leave command to correct a user error:

Node03 was intended to be a manager node. I accidentally added the node as a worker. Realizing my error, I used the swarm leave command to remove the node from the swarm, putting it back into single instance mode. Then, using the manager join token, I re-added the node to the swarm as a manager. Phew! Crisis averted.