Of course, you can search in the bookmarks. Just use the Find button - for convenience, you have the current document's URL and title pre-filled there, and for convenience only up-up-enter-down-down sequence is enough to have the playground clean. Then, just fill a substring of what you are looking for, and the bookmarks will be filtered so that only the matching ones are shown. (Actually, currently it will not be filtered but the cursor will only jump to the first matching bookmark below the current cursor position - and it will NOT wrap around. The exact behaviour changes time by time and hasn't been stabilized yet.)