It's not currently possible but it's in the developers ToDo list. However, you can use a workaround for now for the GTK GUI.
Add a Network column to the Results* tab:
File->Settings->GUI->Columns titles->Results->Add->Network%%% or right click on a column header of the Results tab, then
Add column after->Network
- Search anything you want
Go to Results* tab. Now, you can identify from which network each result comes from.