There is no search button for documents. It is hard to find one document by name when I have plenty of documents. It can be added to menu on the top right corner as another menu option.
search is available when experimental editing mode is activated, but makes sense to also have it available in regular/viewer mode.
Mert Tümer committed a patch related to this issue. It has been pushed to "master": http://cgit.freedesktop.org/libreoffice/core/commit/?id=5f4c120dd4dcc96329a4b0bcd72d76fb37b42fed tdf#96790 search function in non experimental mode It will be available in 6.1.0. The patch should be included in the daily builds available at http://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More information about daily builds can be found at: http://wiki.documentfoundation.org/Testing_Daily_Builds Affected users are encouraged to test the fix and report feedback.