Until now in internal activity allocation, a WBS element could be chosen as a receiver, but not a network/transaction.
As of Release 3.0E, depending on the network planned, posting can take place to the network header or the individual transactions.
To use a network/transaction as receiver in the list screen, you must define a new screen variant in Define screen variants for activity allocation .
In the detail screen of transaction KB21 (Enter Activity Allocation), network/transaction is included under receivers.