@J-M-L I’m not seeing how that library helps, can you elaborate?
As I understand it, the only way to have one setting or memory location for multiple LEDs would be to change the function that pumps out the serial LED data so it can do tricks like that on the fly.
If that is the case, the WS2812s would be a bit of a challenge, with the timing of the pulses, whilst APA102 LEDs, which use a data line and a clock line, would be very straightforward as one can use these LEDs with no memory representation of the entire strip whatsoever. And take whatever time it does…
by using your own SPI interface to the APA102.
You can still use library features if you need to exploit the library tools ability to translate colors &c., just do it on a dummy strip of as few pixels as you need, then pluck the data out for your own on-the-fly calculations.
I used digitalWrite and hand done data transfer, it got better with fastDigitalWrite and of course build-in SPI can be used and is fastest. I was mostly seeing if I could run the APAs w/o any (any) library whatsoever.