Malcolm, it sounds like you want to control which nodes are expanded and collapsed in a given view. You might be able to accomplish something close using the “parent:” operator. I show a use case over in another thread where I use it to create a view that shows open tasks for different projects:
You can bookmark these searches, make links out of them, etc. In your shopping example above, you might be able to use “parent:groceries” to make sure the groceries node is expanded.
I hope this is helpful.