Sidebar page name from which the content for the sidebar gets pulled. This page is usually in the root namespace but you can add different sidebar pages per namespace and the nearest page will be used. This only works if the template supports it. Leaving the field empty will disable the sidebar.
sidebarTemplates currently supporting this setting (other templates might support other forms of sidebars): 20cones, ach, adoradark, aran, benjamin, binkytestinstance, bootstrap3, codowik, dokuwiki, grassstains, greensteel, mindthedark, starter, starterbootstrap1), starterpjax, taratasy, writr, zenlike