Hi I have a variation of this question - reading this thread has been helpful but hasn't gotten me all the way.
I am using a 12 step in toggle mode with a midi guitar controller. I use the 12 step to activate and deactivate midi instruments/sample packs for the guitar to play by mapping each key to the mute/unmute button of a particular ableton track - each ableton track has a different instruments loaded in (e.g. track 1 has a strings sample pack loaded in, and key 1 on the 12 step is mapped to the mute/unmute button for that track; track 2 has horns, and key 2 is toggles the mute button for that track).
I'd like for the LED for each key to represent whether the track it is mapped to is on or off (so when the string sample pack is audible, the light is on; if not, the light is off). The default is for the LED to only go on while the key is pressed down, but otherwise be off, whether the track it corresponds to is activated or not.
I used the idea from this thread above and created a dummy midi track as suggested, and now I feel I'm half way towards my solution: I've mapped key 1 so that it both activates the string track and also activates a midi clip on a different track that makes the key 1 LED remain illuminated. But I can't figure out how to then use the same key to deactivate the LED/clip once I've decided to stop using the string sample pack - in other words, I can turn the light on, but not off. Think there's a solution for this?