It is possible to see all active animals in a location. Before this is possible, you need to add the capacity for each location.  


Go to Settings > Site information > Location.


On pen level, simply write how much capacity is available. Remember to press save for each pen. The capacity for each pen is automatically added up in the capacity field for the section and then in the capacity field for the barn (depending on amount of sections). 


Go to Animal events > Relocation


Start by clicking the "+" icon to register a relocation.


Once you choose a location, a dropdown menu for the locations appear. Here, it is possible to see how much capacity is left in each location.