My understanding of Timer CHOP is that the reason you have to re-init to use a new Length value is so that it doesn’t get messed up if it’s already running (I may be wrong).
Is there a way to make a Timer CHOP use the updated Length value the next time its run without initializing it first?
Yes as soon as you change the length, lots of stuff changes, like timer_fraction.
What you could do is in the onDone() callback is to set the new length there, and the next time it runs, it will use the new length.
You can set the On Done menu to Re-Start to start it right away, or click the Start pulse in the onDone() function, or …