Although there is a reference on IMDb, I suspect that this is not a unique ABBA TV appearance because it's not mentioned anywhere else and it is most unlikely they went to Germany just for one TV appearance.

Most likely it was just showing a PROMO clip, but as the broadcast date is 4 April, so NOT impossible when ABBA went to The Netherlands on 3-4 March they made a short trip to Germany too – but it need to confirm yet.

Cast (in credits order):

1. Ulrike von Möllendorff  (co-host)
2. Gerd Mausbach (co-host)
3. ABBA

Click here for a TV listing from Leidsch Dagblad - 4 April 1975, p5

Die Drehscheibe (Benny), 1967;
Die Drehscheibe (Benny), 1968;
Die Drehscheibe (Agnetha), 1969;
Die Drehscheibe (Agnetha), 1972;
Die Drehscheibe, 1974;
Die Drehscheibe, 1975;
Die Drehscheibe, 1975;
Die Drehscheibe, 1975;

Thanks to Jozsef