You cannot create an activity element in a new network

What causes this issue?

Either in Customizing or by choosing <LS>Settings -> Control</>, you
have stipulated that a new network should be created. At the moment you
are creating an activity element. Hoever you cannot create an activity
element without an activity.

System Response

INCLUDE 'NA_ALLG_NOFUNKTION' OBJECT DOKU ID TX

How to fix this error?

Create a superior activity, or change the settings correspondingly.

Error message extract from SAP system. Copyright SAP SE.