Hi Matthias,
It is not possible to directly play tracks in the CueCore2. The only way to playback tracks is by using them in playbacks.
You can use OSC/UDP to directly jump to Cue's (Which are tracks) in the playbacks.
In Kiosc there is currently no proper way to use this though, so I recommend using custom commands together with ShowControl.
For example:
/pb1/cue1 as TAG, and add this to ShowControl with the task Playback > Jump
If you need more help, let me know!
Greetings,
Bootsy