Hi there, and welcome here…
Did you read the wiki and the power pins if its not spelled out on the rp2040 like on the other xiao’s not sure why . Anyway a diode is needed between 5V external source and the pin as to not harm the xiao.
Check some of the other threads as well on it.
HTH
GL 
PJ 
from the Xiao Esp32S3 for example:
- 5V - This is 5v out from the USB port. You can also use this as a voltage input but you must have some sort of diode (schottky, signal, power) between your external power source and this pin with anode to battery, cathode to 5V pin.
- 3V3 - This is the regulated output from the onboard regulator. You can draw 700mA
- GND - Power/data/signal ground
I do see a caution on the rp2040 Wiki about having both, so read the manual.
and here in the online schematic I do see a diode between Vin and VBUS so there’s that
