If I decide I want, say, an Azure Portal container then I cannot have login.microsoftonline.com assigned to a different container -and- configured to automatically open in that container.

If I do that, I need to have a combined Azure + Office 365 + anything-I-need-to-authenticate-to-Azure-AD-for container.

It’s a good solution but with its lack of flexibility I find it’s too far in the direction of security versus convenience.