It seems that LibreOffice does fallback to an own GUI if libreoffice-gtk is not installed (as shown here: http://img1.picload.org/image/lggcpai/2013_12_30_23_31.png). But on the file dialog hidden files are not shown and there is no such context menu like on GTK+ which has the option to show hidden files. Maybe the fallback menu can be enhanced to contain such an option too.