It would require Omio's email for bookings, does anyone have it/would this even be possible?
This simply isn't how the reservations system works, so no it's not possible.
In theory, an operator could amend a reservation using the 8 character code written on E-Tickets (e.g. AA123456), but this is only supposed to be used when a train type changes in the timetable (a "set swap").
This doesn't automatically change the seat information elsewhere in retail systems, such as in booking details on the retailer site, the E-Tickets, paper tickets, etc., hence why it shouldn't ever be used other than these circumstances, and can be the cause of scenarios where two people appear to have been double-booked the same seat.
Anyone had better luck, I thought I remembered reading here that support could help, but given Uber's atrocious service in general maybe it's too much to hope for?
The original retailer could, in theory, change the reserved seat, but many won't have tools for this so it will simply not be possible for frontline staff to do.
The customer support for the forum's ticketing site would usually just book a new seat instead as it's much easier than trying to amend your existing seat.
I would like us to offer the option to amend your existing seat in the future, though!
Getting a seat allocated for car parking, now that would be something...
@trient's link ("have a
tool to modify a booking") is about managing an NCP car park booking rather than anything ticketing related, as given away by the huge NCP logo in the corner of the screen.