The app Enter Direct Activity allocation allows to post both positive and negative values, however, this app turned obsolete.
S/4HANA Cloud - CE2011 and upward.
The app Enter Direct Activity do not exist anymore.
The functionality to post negative quantities is available with the new app Manage Direct Activity Allocations
negative value, Enter Direct Activity, Manage Direct Activity Allocations, F3697. , KBA , CO-OM-ACT-E , Postings , Problem