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 became the head coach for the Flemish Judo Federation. Before this position, he had led the British judo team and served as a coach for both the Austrian and Qatari teams.