DB have introduced a "Komfort Check-In" service on some trains where you can indicate that you have sat in your reserved seat by using the mobile app, meaning that train staff do not need to disturb you during the journey
https://www.bahn.com/en/view/bookin...04_S02_D002_KIN0061_NAVIGATION-LINKS-KCI_LZ01
https://www.bahn.com/en/view/bookin...04_S02_D002_KIN0061_NAVIGATION-LINKS-KCI_LZ01