The CONTAINS function is the most robust option outside of STARTSWITH and ENDSWITH. I know the methods you've given are generic examples but they can be shortened a little:
Because it's a boolean, Tableau Desktop adds the if/else logic automatically.
As a rule of thumb, if you can't find a function in the product manual, it's a safe assumption it's not a feature of Tableau Desktop. There are a few exceptions but there are very few of these and they are usually detailed in the community or on partner pages.