One of the rail travel tricks I often use is making a reservation in a different app from where I bought the ticket. For example, for some international connections it is not possible to reserve a seat in the DB app, but I want to buy my ticket from DB to get bonus points, and I want to have a guaranteed seat (happened when I was travelling to Pilsen for Easter). Also I use local apps if I have to take another train than stated on my ticket for whatever reason.