Hi Albert,
In order to perform the activity to remove the node from cluster, login to leader and navigate to configure >> Cluster and planes. We can see the list of nodes in the cluster, can disconnect the node from GUI, by clicking the “red minus” button and then confirm it. Just make sure to keep all nodes in the cluster online before removing the node. The APs managed by removed node will join the existing cluster and continues to operate without any issues.
Cheers
Ravi Teja