You cannot shift the initial element

What causes this issue?

You are currently working with only a portion of the work breakdown
structure. In this situation you cannot change the assignment of the
WBS element (initial element).

System Response

INCLUDE 'NA_ALLG_NOFUNKTION' OBJECT DOKU ID TX

How to fix this error?

If you want to work with all WBS elements in a project, you must enter
the key for a project definition on the initial screen.

Error message extract from SAP system. Copyright SAP SE.