Your sequencer can only be assigned one midi channel number at a time per channel you’ve tasked with controlling mutes, and each digitakt track will require it’s own unique midi channel number to successfully be individually muted.
So, from your external sequencer you would have to assign the correct midi channel number to match the individual digitakt midi channel of the track you want to mute, then if you wanted to do another one you’d have to change the sequencer channel to match that track, then in order to disable the first mute you’d have to change back to the first midi channel.
That’s how you would control all mutes individually from one sequencer channel. The other solutions proposed suppose that you want to mute all at once from one sequencer channel, that is setting all tracks to the same midi channel and then sending one command from your external sequencer to mute, and then sending it again to unmute, it affects all channels at once.