yes, it’s true, the powerboost has the EN pin, but as I said in my post, the idea is to do it without a manual switch.
In the event that XIAO does not support 5v and USB at the same time, I would try to do it using MOSFETs, but I must first know if XIAO supports 5v and USB at the same time, I only have one XIAO and I don’t want to damage it. thanks for your answer