UPDATE: Report Builder updated how it requests the data slightly. You can still use the approach from this video, but the information will be slightly different in a debugger.
In a debugger:
1 - Search for api5.omniture.com. The number might vary from 1-5 depending on your data center.
2 - Go to the Request tab
3 - Search for 'Report.Queue' in the request.
There is also an alternate method to debugging requests like this, and it works just as well. You can turn on Report Builder logging from the Options mene and that will record the same information as a debugger would. Logs can be found under Documents/ReportBuilderLogs, and will be organized by day. You can search the file for 'Report.Queue' to find each of your requests. Logs also help with troubleshooting any issues.
For more information on this feature, visit the documentation.