Bookmarking reports is a great way to group the reports you need frequently.
To group your most frequently accessed reports together just click on the "Star" icon next to the report title and you are done!
All bookmarked reports are now saved under the "Starred Reports" section in your side menu for easy access. To remove a bookmark, simply click on the "Star report" icon again.
Alternatively, you can mark your report as Starred by clicking on star icon next to the report name under "My Reports" section in side menu.