The SharePoint designer file "->" new "does not contain" workflow"

Overview:
I want to design a workflow in designer, but when I use designer to open a specific website, no workflow is found in file --> creation, it took me an hour to find a solution to such a small problem, and I shared it with my friends to avoid detours.
Solution:
In this case, because your website adopts form authentication, you need to change your authentication to Windows Authentication during workflow creation, then you can use designer to open your website and design your desired workflow.