For browsing a tree, you can use the presentation property "Specify a root object to be shown in the chooser", and attach the "Templates" folder to it.
For the list case, you can the presentation property "Predefined list of elements", and attach to it an action that returns the array of elements to populate in the list.
Yes. It's the "attach" part I was having trouble with.
(with the help of my TAM) I created a variable "#templateFolder", type VC:VmFolder and set to Templates.
Then in the Presentation, Predefined list of elements