You can hide and unhide the clusters by performing the following steps:
Check the Show/Hide checkboxes corresponding to the clusters you want to hide.
Click Hide. The selected clusters can no longer be viewed on the AWS Configuration screen.
If you want to unhide the hidden clusters, go to Welcome <username> > User Preferences.
Check the Show Hidden Items checkbox to unhide the hidden items. The hidden clusters will be displayed back on the AWS Configuration screen in disabled form.
Select the disabled clusters and click Show. This allows you to restore the hidden clusters.