The Admin should be able to select/deselect page blocks that will be available for an Editor when creating/editing content.

When an Admin deselects a block, we will show a warning message. 

1. When the blocks are not categorized then the warning message will be displayed under 'Select Block(s)'
2. When the blocks are categorized, then the warning message will be displayed under the categories base on which block was deselected. For e.g., If Admin deselected the Targeting block under Default then the message will be shown under Default. 

Prototype - https://projects.invisionapp.com/d/main?origin=v7#/projects/prototypes/21058682