The BLF A6 had a rudimentary version of this, it used the decaying voltage in a charged capacitor to measure the time that the power was interrupted. This let you do a medium press to go backwards. It’s a great feature of the UI that I really miss in other mechanical switch lights. There’s a modified version of Bistro UI that uses the off time memory in the MCU to measure the switch timing directly, which is more reliable as it doesn’t change the decay rate due to temperature. I’d love to see Bistro HD (as it’s called) ported to some modern drivers, I’ve had a little look at doing it myself but am a little out of my depth trying to port code written for an attiny13 to an attiny1616, let alone then implementing it in a boost driver or something!
There’s a thread on the Bistro HD here: [UPDATE:v1.7.1,Q8&1chanOTSM]bistro-HD, bistro your way. OTSM, eswitch(devel), Vcc reads, safe_presses, turbo timeout...