Q:

How to Add contacts to an Event or Membership from the Search task list

I am sure that Advanced search results used to provide the Actions of 'Add Contacts to Event' and 'Add Contacts to Membership'. 
But I can't find any reference to this in Civicrm 4.7, neither in our site, nor the demo sites - nor the current literature. 
I'm on 4.7.27, Drupal latest.
I found these earlier references to Add Contacts to Event: 
https://docs.civicrm.org/user/en/latest/events/manual-event-registration/
https://issues.civicrm.org/jira/browse/CRM-1988
I've also looked in Drupal Permissions without seeing anything obvious there. We're not using ACL. 
Any ideas whether these two features are still available? They'd be massively useful to us.

A:

'Add Contacts to Event' was renamed to 'Register participants for event'
I don't recall an 'Add Contacts to Membership'

