Soizucat69
In Switzerland, seat reservations for individuals are only possible on IC (InterCity) and EC (EuroCity) trains (though not necessary at all in most cases) and mandatory for a few selected “panoramic” tourist trains.
The trains to Engelberg are IR (InterRegio) trains, so reservations are not possible, excepted for groups. Those coaches are not numbered (for sure), and the seats inside might also not be numbered neither (not sure here, as we Swiss are basically never reserving train seats, and therefore are not used at all to check the seat numbers!)