When the new General Ledger is active, can I still use the old functional area derivation for event 0005 (filled after the document entry view) instead of using event 0006?
You can continue to use the old derivation of functional area according to event 0005. There is a switch in Customizing that makes it possible to use event 0005 in the new General Ledger. Choose the following path in the implementation guide: Financial Accounting (New) -> Financial Accounting Basic Settings (New) -> Tools -> Customer Enhancements -> Enhance Determination of Functional Area In this Customizing transaction, deactivate the indicator “Determine FArea on Entry Screen”. For detailed information, see the field help (F1) for this field.