System_ON_Sleep of XIAO BLE

The reason for reserving two bytes for Peripheral number is that I wanted to put the identification number in the upper one byte in case the experimental CID = 0xFFFF duplicates with other experimental devices.
I am currently experimenting with using scan response to increase the amount of data that can be transferred. I am reading the bluefruit library very hard but am struggling. Do you have any tips on how to do this?