The data entity "Project ledger posting definition" allows to export data, but can only be used to import data once.

As soon as data has been imported no updates to the existing records are possible. This error is shown:

"Cannot create a record in Ledger posting setup (Projosting), Account type: Cost, The record already exists."

Other data entities like "Ledger posting definition for procurement" allow to update existing records. This should also be possible for the data entity "Project ledger posting definition".