Bring up the Troubleshooting panel.  Enter the following:

netflow:network:{SrcK8S_Namespace="netobserv"}

Add an extra newline character after the above text.  Click "Query".  Now click the "Network (000)" node.  It brings up the Observe > Network Traffic, Topology tab.  In the filter, it has "netobserv"}.  Note the extra } (see attachment).