Saving as Unread
"Read later" is the option that allows you to save a bookmark to your library as "unread" so even if you don't have time to read something now, you can easily find and read it later. There are two ways to save a page as unread. The first is to simply click the read later icon on the Diigo menu. This saves the bookmark with default settings as well as saving the bookmark as unread. The other way to save a bookmark as unread, is to bookmark the page by clicking "Save" on the Diigo menu and checking "Read Later" on the bookmark options dialog.
When you want to find and read your unread items, simply click "Unread" in the Diigo menu. Your library will open in a new tab, filtered to show only unread items.