You may favorite any dashboard that you created or is shared with you.
You may not “delete” dashboards created by others. However, you may simply unfavorite what is shared with you to remove them from your usual lists.
Steps
9. Go to DASHBOARDS > Manage.
10. Click the Favorite icon.
11. To un-favorite, click the Favorite icon.
Example
Go to DASHBOARDS > Manage. Click the Favorite icon next to New Dashboard. Then go to the Favorites tab.
Un-favorite New Dashboard by clicking 
Favorite
again.
Now it is removed from the Favorites tab.