Having a dedicated command was also suggested by BitArts a while back:
I was first having a go at QCx (x = tick) as a pattern effect. It would be quite ‘consistent’ with current pattern effects. Q normally is delay, but has a wide range that’s unused. It makes sense to me, unless you want to bring in a completely new dedicated effect number.
For reference, when importing xm modules, Kxx should be remapped to such a note-off effect 