Q. Is there a way to query multiple networks in the Flows window?
A. No, you'll have to create a CIDR block that includes both subnets.
For example, if they are contigious, that's easy:
10.20.30.0/24
10.20.30.1/24
Can be grouped as:
10.20.30.0/23
If they are further apart, it might be harder to do that, or two separate searches must be used.