All Network Nodes will have an action that will allow you to either remove or exclude it from the topology, as seen here:
The main difference between excluding a Node vs deleting it is down to Node persistence across discoveries. In other words:
Deleting - The node is deleted from the Topology, however a new discovery may find it again and bring it back.
Excluding - The node is deleted from the Topology and blacklisted, hence no further discovery will find it again until the user whitelists it.
After being excluded a the IP referring to the Node will show up in the Excluded Subnets section of the SNMP Configuration section, in the Admin page.
You can then edit the config and remove such IP from the excluded list to potentially find it again via a new discovery.