Comment 34 for bug 1547949

Looking at the code shows that this is caused by lines 98-103 in main-toolbar.vala:

        // FIXME: This doesn't play nice with changing window decoration layout
        GearyApplication.instance.config.bind (Configuration.MESSAGES_PANE_POSITION_KEY, this, "left-pane-width", SettingsBindFlags.GET);
        bind_property ("left-pane-width", folder_header, "width-request", BindingFlags.SYNC_CREATE, (binding, source_value, ref target_value) => {
            target_value = left_pane_width - 43;
            return true;
        });

This code fragment insures that the search toolbar and reply and so forth buttons stay centered at the slider.
This needs to be fixed.