As an admin I want to be able to select all screens, using single checkbox, for Custom Fields

Problem Definition

Currently, there is no option to select all screens, in a single checkbox, for a custom field. This could especially be a problem if the admin has a large number of screens and he has to select them one by one. The following screenshot better explains the problem:

Suggested Solution

Have a select all option at the top of the list, that will automatically select all screens for that particular custom field.