Hey, I think
sustain does what you are looking for.
d1 $ n "0" # s "midi" # sustain "<0.125 0.25 0.5 1>"
This will change the note length at every cycle as expected. My problem with
sustain is that it's parameters are in seconds which is kind of hard to manage if you want musical note lengths like quarters or eigths etc.
Regarding my original question I'm in serious doubt. Now I tired it out with Yoshimi on my home computer and it seems that it actually ends the notes as expected at the end of each event. In my studio where I use hardware synths I experienced it otherwise, but that might be the result something not Tidal related.
Thanks and sorry if my question did not make any sense,
[Edit] I checked it and Tidal definitely sends the note-off event after the end of the Tidal event. My bad.