Quellmalz was appointed head coach of the Flemish Judo Federation in 2022. He has previously directed the British judo team and served as a coach for the Austrian and Qatari teams.
In 2022, Quellmalz took on the role of head coach for the Flemish Judo Federation. Prior to this, he had managed the British judo team and served as a coach for both the Austrian and Qatari teams.