well I digged around zypper and found this

use "zypper lr" to list the used repositories and they exact name

use this name in a line like

zypper se -i -r multimedia:apps to get

Chargement des données du dépôt... Lecture des paquets installés...

S | Nom  |Résumé                        | Type  
--+--------------+--------------------------------
i | cdrecord     | A CD/DVD/BD recording program       | paquet
i | libscg1_0    | An OS-independent SCSI transport library | paquet
i | libschily1_0 | Support library for SING utilities  | paquet
i | mkisofs      | A program to generate an ISO-9660/JOLIET/HFS/UDF hybrid filesystem | paquet
i | shotcut| A free, open source, cross-platform video editor|paquet

that is exactly what I wanted

and -s gives more data