Hi Veronika,
I think there's a misunderstanding. Whether a trip is a travel request or an expense report solely depends on the ANTRG-status. I.e. you can indeed use S_AHR_61016401 (although it's below "expense reports" in the infosystem) and select for all trips with status ANTRG = 1 or ANTRG = 2. This way it will only show trips that are currently in request-mode.
Cheers, Lukas