There is no requirement to save or confirm changes to an existing collection when you edit a collection. In fact it's kind of spooky how easily they get created. I've created several by accident when I was just poking around trying to learn the feature and didn't realize I'd left these scattered sandbox collections around. It's easy enough to delete them, I know, but I expect to have to save it before it actually gets created. I guess this is an aspect of L4 I haven't gotten used to yet, because everything else user-generated works that way too. Perhaps most users find that easier to use and they like it?
But the danger of this approach is that it's also too easy to accidentally obliterate a collection you'd set up, if you think that by typing in a new name and a new rule you will create a new collection. You can't just go to your already open Collections tab and start creating a new one just like that. You actually have to click New first to get a new "Unnamed Collection" and then you can begin to type a new name and rule.
Which is worse? Having to save after setting up your collection (and of course being reminded to do so if you try to close the collection before saving it, the way Windows apps have worked forever), or having garbage collections show up unexpectedly ("Unnamed Collection (2)" and "Unnamed Collection (3)") and being able to accidentally overwrite an existing collection too easily with no warning?
Is this an issue that only an experienced geek would ever run into? Sometimes I need a reality check!