ios Shortcuts: get index of selected list item
Based on the comments, this Apple Support site held the answer.  Use &quot;Set Name&quot; to get the value:

To set a custom name for an item that an action outputs, such as an
image in the Get Latest Photos action, place a Set Name action in
between the Get Latest Photos action and the Choose from List action.
When the shortcut is run, the custom name (rather than the default
name, such as “IMG_0365”) is applied to the image output from the Get
Latest Photos action.
If you use the Choose from List action with the Dictionary action, all
of the keys in the dictionary are displayed when you tap “Add new
item.” For each key you select, such as Number, Boolean, or Array, the
corresponding values are passed as output.