I'm starting to work with Smile custom dialogs. I can figure out how to get
data into the "menu" dialog items. But I can't figure out how to select a
particular item by script.

If I repopulate the menu, I generally want to select the first item in the
list. How do I do that?

Set menuItemList to {"A","B","C"}
set theMenu to dialog item id 198 of  theDialog
Set menu of theMenu to menuItemList
-- ??? Doesn't work:
Set selection of theMenu to item 1 of menuItemList