Grouping accounts

For those of us with many email accounts. To group email accounts into sub-groups. like Business, Personal, Important. just as an example. The subgroups should be self-determined, not fixed. Over half my email addresses are not shown, without scrolling, before the Manage Folders section on the left. It's a PITA. But if they were sub-grouped, you could hit on the subgroup and expand the email addresses according to a defined category, or hit it again to close it. It wouldn't need a Unified Account for the sub-group. So my suggestion would look something like this......
Unified Account
Subgroup A
Subgroup B
Subgroup C
a@nemail.com not defined into a subgroup
b@nemail.com not defined into a subgroup

If no sub-group is defined, then it would look just like now.