angular ui-router maintaining state of subnavigation menus when moving around a SAP

I would like to know what the best way of preserving which sub-navigation area a user was previously on when moving between different top-level nav areas of a SAP angularJS application.

At the moment I have some code in the $transition method which updates a map which stores which sub-content to load for each header menu was selected, it then intercepts the transition and redirects using a $state.go statement rather than directign the user to the default for that section of the webpage. I am not keen on for maintenance reasons because it overwrites the sref of the top-level nav bar, but I am not sure what alternatives there are.