When you click on the type of parameter on the execution block, there will be a drop-down list of different parameters to choose from. One of the options is Browse that will popup a PickType window allowing you to select a type for your parameter. You will need to know the namespace where the type resides to select it. For your example, you can find the String collection under the namespace System.Collections.Specialized. If you are unfamiliar with namespaces of a type, you can find them on Microsoft docs.
Hello, I also have this issue. Your suggestion to use a Strings Collection does not work.
We would like to be able to pass a variable number of strings, in your suggestion it is only possible to pass a collection of strings already formed as a list. We would like to be able to pass multiple strings and the execute method would expand automatically as you enter them, much like the String Utils function.