Due to limited staff during the holiday period, we unfortunately can't handle your case before we get back to thenormalstaff by the first week of January 2019. We are sorry indeed for the delay. We wish you a great holiday and a Happy New Year 2019.
If you download nRF Connect Desktop on your computer, you can add characterstics to your device through a serial interface. See this link for more information.
However, I would recommend you to implement it yourself, here and here are some nice tutorial that demonstrates how to create custom characteristics.
