The button in your screenshot is from a theme component, it’s a feature of Topic List Excerpts
You can actually have both enabled at once, but it doesn’t make much sense… so I recommend not doing this (the checkbox can be disabled in the topic list excerpt component). Better to choose either excerpts or AI gists.
This was outdated, but I just made some updates — @DonBot feel free to follow that guide now and let us know if you encounter any issues.