That’s no problem. The mobile pass is your ticket and the reservation is separate from the pass. You don’t need your BankID to make reservations online though.

Here are guidelines on how to make reservations.

https://community.eurail.com/train-connections-reservations-47/how-to-get-reservations-105

You can also book by phone, e.g. using DB, ÖBB, SNCF.

NOte-for deg Svenska: it seems the Swedes delight in having these new virtual only cr/bank cards. Be aware that in many counties in EURope they are not that much advanced and these cards will not work-or certainly not anywhere and small purchases in many countries are cash-only. That plastic small VISA or so card is best to take.