Can I chain multiple Use AI columns in a waterfall?

You cannot repeat the same AI action type in a waterfall, but you can use different AI models or actions in sequence. For your specific use case of trying Gemini first then 4o-mini, it's better to create two separate Use AI columns rather than using a waterfall. If you want to try the same prompt with multiple AI models until you get a result, set up separate columns with different models rather than chaining them in a waterfall. Reference: documentation