Unfortuantely, OpenSpan does not support multi-tab functionality for browsers. You will need to have the report open in a new window to successfully automate the report. I would suggest to use the navigate method with two parameters. The first parameter is where the link to the report should be provided, the second paramenter allows you to set true or false. True allows the navigated page to be opened in a new window, while false opens the page with its default behavior.
I can see that this is a very old post. My requirement is to open multiple webpages in a single window, although the pages will be from different web adapters. Can this be done now? Has there been any development on this from Pega side?