As part of #1875252: [META] Make the block plugin UI shippable, we've looked at having block "categories" to help sort and filter blocks, somewhat like how Ctools currently handles categories.
For an example of this functionality, see https://projects.invisionapp.com/share/6AESEWGY#/screens/7279853.
This is a stub task to add the custom category information as illustrated on that mockup.