Creating a parent dimension within an existing UD Attribute

Hello! 

Sure it's possible - you would just insert a new child under Line_of_business then move those three children under the new parent.

Regarding reporting, you'll have to consider how reports are set up around these members. For example, if you have a CV that's pulling Line_of_business.children, it's no longer going to be clean with just the lines of business. It's easy enough to fix that - just some manual cleanup that might need to be done after you make this update. 

The first suggestion is another possibility too, depending on how you do your reporting - an alternate hierarchy so your current structure is untouched but you have another structure with just the new parent and the three lines shared underneath it. 

Hopefully that makes sense but let me know if it doesn't.