Making a new assistant, you can't create a custom bang for it unlike !code
.
Relatedly, you can't make custom bangs in https://kagi.com/settings, only in the search interface.
I created a custom bang !summarise-jp
which is meant to summarise a japanese article I'm reading. I set up custom assistant for it, and then typing in the query !summarise-jp .....
in Kagi search will redirect me to the assistant.