Actually, you could've used Snippets.
No, as I understand snippets, they "let you store content for quick reuse". That's right out of DW's Help. If you've got some code or object or something that you use a lot you can use snippets.
I was only looking for a way to temporarily make portions of of an html page code (which would include text that is displayed on the page) collapse or be invisible for the purpose of making it easier to see what is going on in the page.