ashamed to ask...

[bealefay]

I assume it's something simple I'm missing, but how do I create a new collection (say, "Vacation") in the Navigation pane?

[Zantara]

Please don't be ashamed for asking a question.

I haven't been able to discover how you can add a new collection to the navigation menu other than adding a smart collection based on a date range i.e. your vacation
You can add a folder you created yourself called Vacation through Folders > Browse more folders

But that's not quite what you had in mind, is it?

[Jean-Luc]

If your vacation images are tagged, you may use Add Smart Collection which is able to create a smart collection with all images containing the tag Vacation.