Thanks for the precise answer man, it clears al the doubts I had.
At this point, if you have a multiple matrix setup, and you need to frequently update the code inside the boards,
I think the best procedure is to chain the boards with 5cm cables between the power and I2C pins,
instead of short and fixed shits, so you have some space to plug the USBuart
while keeping all the other connections plugged.
Now I just have to understand how to convince the pixels to do exaclty what I want,
but that’s another story…
Muchas gracias indeed,
have a bright day,
bless,
kk