SharePoint Flex contains a default list called “Leads” which was established to contain records that should stay separate from the main Account/Contact lists.
The purpose of the Lead list is to maintain a location for unqualified prospective customers to stay until they can be qualified and converted to an Account item with a Contact and an Opportunity (optional).
The Leads list has a more limited set of Sub-Grids available (No Contacts Sub-Grid) in comparison to the Accounts List. The Sub-Grids appearing on the Leads Display Form include Interactions, Tasks, Calendar Appointments, Emails and Documents.
Additional Sub-Grids should not be added to the Leads list. If you require additional Contacts or Opportunity items than can be configured in the single Lead Item using column fields, set up an Account as a “Lead” type.