Dropdown list block

I have two drop down lists. One has a list of if items like A, B, C, D etc. When the user selects an item in this list, I want a second drop down list to show items based on selection from the first list. How is this to be done. Any ideas?

This is not currently possible with the built-in Input Controls block. A workaround that others have done is to build a custom block using Experience Views and then embed it into your dashboard using the External Website block.