Allow creation of custom investment account groups for Dashboard and Portfolio [EDITED]

I recently discovered a feature that allows users to select investment accounts to get introspection of only the selected accounts. I.e. the "Dashboard" only shows the securities for the selected accounts. This feature is very nice. Tt would be super helpful to be able to save these groups so the dropdown would allow the saved group to be selected. The dropdown now contains "All Investing Accounts", "All Brokerage Accounts", "All Retirement Accounts" above the line and then list all accounts below the line.

The saved group feature I am requesting would allow me to select a number of accounts. An example would be selecting all my managed accounts and then creating a new group called "All Managed Accounts". This new group would then appear in the dropdown so it would then list "All Investing Accounts", "All Brokerage Accounts", "All Retirement Accounts", "All Managed Accounts" above the line.

[Title edited to better describe the request. — jacobs]