The goal of the Drafts Container functionality is to allow users to approve the Part and its Master CAD Documents without being delayed by the finalisation of the other "secondary" objects that are related to the Part but not relevant for the approval of the Part. On top of that, this functionality allows users to attach "secondary" documentation to the Part at any lifecycle state.

The Drafts Container must be manually activated from the Part Profile Card. You just need to select the   icon and choose “Activate Drafts Container”. 

Complete description: Drafts Container FAQ.