we make use of custom properties to select the nodes that need to be backed-up in each job.
[we have another job that select items where the Last Login Result is not 'Login OK' that we use to catch transient failures in the backup process -- this truly is a dynamic node selection since it's the backup job that catches all nodes that failed to be backed-up in previous jobs due to credentials/authentication issues]
(or have I misunderstood the issue?)