it’s there:
https://hub.youthpowercoalition.org/admin/site_settings/category/all_results?filter=close%20message
In 2.7.0.beta1 ( ee9ea20d95 ) there is another parameter for private messages 
Could you try this link:
https://hub.youthpowercoalition.org/new-message?username=hubbot&title=Hey,%20I%27m%20ready%20to%20start%20my%20new%20user%20tutorial!&body=Directions:%20Just%20click%20the%20blue%20Message%20button%20below%20to%20tell%20@hubbot%20start%20tutorial