I wonder if my original post over-explained (and therefore complicated) the issue. Here’s a simplified explanation:
We have collection items that we don’t want to expose to searches. It seems that the only way we can prevent that is to mark them as ‘Drafts’. However, when we mark them as Drafts, their dynamic item pages aren’t available for Preview.
Because the pages are complex, it’s important to us to be able to preview them before publication.
The only option we can think of is to temporarily mark an item as ‘Published’, preview it, and then set it back to draft.
That’s not ideal, but we’re wondering if anyone has a better approach.
I was hopeful with Ido’s suggestion, but it appears that test sites don’t allow different versions of data collections items.