Are you ever printing this "report" out? If not, then why not just have the script find for the category you want from the dropdown. That way you're not navigating at all.
Since subsummaries do not exist in browse/preview until a layout is sorted, they're not really addressable by script.
What you would need to do is a simple loop script that goes to records until you reach a record that matches what you're looking for. then stop.
Set Variable [ $cat ; Table::globalCategorySelection ]
Go To Record/Request/Page [ first ]
Exit Loop If [ Table::Category = $cat ]
Go To Record/Request/Page [ next ; exit after last ]
Boy, that was fast. The loop worked great, thanks. I used a Record/Request/Page [Next] after the End Loop to move the list up, is there a more elegant way to move the list up instead of adding a bunch of Record/Request/Page [Next]'s at the end of the script.