Currently, you can not save a chart created within AI chat. Domo is working on adding that functionality. Your alternative would be to create a new dashboard and use the Domo AI Content Builder Agent. You can select the dataset that was used in the AI Chat and then ask the same question. It will likely create multiple charts for you, but will likely create the one you saw in the chat.

You can access the AI Content Builder Agent by going to Apps and click the drop down.

There's a video to walk you through it at the top left.

But I don't know how you give it a custom question against the dataset.