If you want to create a new Host based on an existing one, click on the contextual menu of the Host you wish to copy the settings of and select 'Clone':
This will load a new 'Host' modal with all the pre-populated data of the original Host.
In the above example you will notice that the 'Host Title' field is highlighted in red as there is a conflict, in that the 'Host Title' field is not unique. Change the 'Host Title' and any other definition of this new host and click Submit Changes. The new Host Check Command will appear in the list of all Host Check Command's and will be highlighted yellow to indicate that you need to go to Configuration > Apply Changes to make the changes live in your production system: