Hello Jay,

You can use a local list to create your custom options and use them on the dropdown, just make sure that your custom structure has a Value field.

Then you can populate your list.

In this case, I'm using the "OnInitialize" event to add my options to a local list. 

If you already have a list with data you can still use the ListAppend Action to add your custom options to the list by using it on the OnAfterFetch Action for the action where you populate your List.

The Result

I will leave an oml with the code if you need it.

Hope it helps!

Paulo Rosário