To add custom GATT RPC commands

Hi, I’m using GATT RPC commands and setup the device.
Is there any entry I can add custom RPC command and calling functions I wrote?
Thanks!

  1. My goal is:
    Add custom GATT RPC commands and calling custom functions.

  2. My actions are: N/A

  3. The result I see is: N/A

  4. My expectation & question is: N/A