The past time I was frustrated about all the standard Column Names in the Monitor Dashlets. Finaly I had the time to figure out how to remove the standard and "Custom" made Group Column Names for the Dashlets.
If some one else wants to empty the list, then here is how you can do it.
On your VSA server open Microsoft SQL Server Manager Studio.Go to Databases and open ksubscribers
Go to Tables and search for dbo.monitorCollection. Right click on the dbo and click on "Edit Top 200 Rows". The window that will open will have all the Group Colomn Names that are available. Select the rows that you would like to remove and right click and press Remove.
When you now go to you Dashboard List an edit a Dashlet and click on Filter you will only see the Column Names that you left in the dbo.monitorCollection.
Hope this will help you guys.