That toolbar is only shown to super admins and is meant to help diagnose issues with your social meta tags (Open Graph & Twitter Card). The Create Post functionality lets you easily push the current page, along with a message, to any social channels you've created, like Facebook Groups/Pages, Twitter Streams and LinkedIn Company Pages.
In the 6.1 release, later this month, there will be an option to disable completely, even for super admins. For now, to completely disable right now, please edit the /components/com_jfbconnect/libraries/toolbar.php file. Around line 17, you'll see:
public function onAfterDispatch()
{
if (JFactory::getUser()->authorise('jfbconnect.channels.post', 'com_jfbconnect'))
{Update that by changing the if statement to 'false' like below:
public function onAfterDispatch()
{
if (false)
{Do the same for the onAfterReturn function at line 44.
I hope that helps, but if you have any other questions, just let me know.
Thanks,
Alex