It would be nice to add the checkbox option (in /admin/config/user-interface/admin-toolbar-tools) to hide\show toolbar-item-administration-tray on by default (on page load)
and in admin_toolbar.js
if(settings.toolbar.collapsed) {
$('#toolbar-item-administration').removeClass('is-active');
$('#toolbar-item-administration-tray').removeClass('is-active');
}
Active
3.4
Code