Yay, someone's making a version that can be used in Ableton Live! Just under two months ago I was playing around with the Launchpad and was able to change the side LED's light with a little C++ program (https://twitter.com/vdscratchy/status/8 … 2530998274), but I haven't been able to figure out a way to apply it to Max for Live due to technical limitations... It looks like you're rerouting the MIDI output externally through loopMIDI to allow sending the SysEx messages Live blocks, but unfortunately, the software of choice makes it incompatible with macOS (since loopMIDI is Windows-only), if you'd like I can help port it for macOS?
Really cool! Could you share some insights on how you made it and how it works? Don't have time to check myself atm.
Normally, Ableton Live wouldn't allow the side LED to change colors by using notes, however your computer (actually any MIDI device) can send System Exclusive (SysEx) messages to your Launchpad to control any light on the board, as well as syncing it to a tempo, setting it to flash or pulse a light, and my favorite: even display scrolling text. The Launchpad Pro Programmer's Reference Guide tells us a lot of information about the Launchpad essential for developers, including the SysEx message we'll need to control the lights (page 20).
Live restricts the user from sending SysEx messages, as a security feature, which in turn blocks our access to the side LED. So if we're blocked off, how does the hack work? We set Ableton Live to output to the loopMIDI Port instead of our Launchpad (which we've configured loopMIDI to route to our Launchpad), and the Max patch created listens for a specific note (E8) and sends the proper SysEx message instead, which loopMIDI passes to the Launchpad. Side LED fun forever!
It's possible that I missed something important or am giving incorrect information, my main computer is in repair, so I am unable to actually try it out (although I can see everything in the Max patch and view the configuration in Live). But, I hope that I wasn't too confusing, and am happy to answer questions and clarify!