3737289 - S/4HANA Fiori app MTE: how distinguish between Save and Save & Submit and how to access customer own fields

Certain error messages shall only be raised when the user clicks on 'Save and Submit' or only when user clicks on Save. It is unclear how to distinguish between these scenarios in customer own code in BAdI. In particular, if the user clicks on Save,  the BAdIs of enhancement spot FIN_TRV_ENH_TRAVELEXPENSE are only called when there is a change done before. If the user clicks on Save a 2nd time without doing a change to the trip, the BAdIs are not called anymore. 

S/4HANA Fiori app My Travel and Expenses for Business Traveler and My Travel and Expenses for Assistant.

KBA , FI-TV-ODT-MTE , My Travel and Expenses , FI-FIO-TV-MTE , My Travel and Expenses , FI-TV , Business Trip Management , Problem