Hi, Olivier.
Unfortunately, I think my answer is going to be about the same as what I wrote this other topic about “Multiple VL53L1X and memory problems”. The full API is just too big to be able to fit more than one sensor object into memory on a standard ATmega328P-based Arduino, so if you need to use it to change the ROI, you might need to consider a controller with more memory.
Alternatively, ST provides an “Ultra Lite Driver” that you could look into, although we have not used it and I am not sure whether it supports configuring the VL53L1X’s ROI.
Kevin