what do you mean autohide?
#Bookmark bar auto hide
river galleon
just your bookmarks, not the toolbar/urlbar its self?
check
browser.toolbars.bookmarks.visibility
as well as
zen.view.experimental-no-windows-controls
If you want to fully hide the Bookmarks Toolbar, you can change these settings in
about:config`browser.toolbars.bookmarks.visibility` = `'never'`: Never show your Bookmarks, revert by changing value to `'always'`. `zen.view.experimental-no-window-controls` = `'true'`: disable hovering window controls in Single toolbar layout, effectively remove access to the Bookmarks Toolbar.
river galleon
is compact mode on?