Thanks for the clarification!
If you don’t need the text on your confirmation button to change dynamically, I would suggest just setting the ConfirmButton Text property in the designer rather than via blocks. I.e.
If you really need to set that text dynamically via blocks then you need to set the ConfirmButton property to an object that has a Text property set to your confirmation text and a Dangerous property set to whether or not confirming the alert should be considered a “dangerous” operation. Here’s an example:
Sorry for the complexity and the fact that this is not mentioned in our documentation.
Hope this helps!
-Mark