I want to connect 6 audio channels with Jack. But I can see only 4 channels in the jack interface. Puredate and Jack run on Windows 10. Has someone the same strange problem?

@ecotec Asio4All is recommended for Pd and could resolve your problem......
...... its a very useful driver anyway in all circumstances..... allowing you to use multiple soundcards with a different setup for every program.
https://ccrma.stanford.edu/software/jacktrip/windows/index.html
...... specifically for JackTrip but still relevant.
David.