Custom Entities will need to have a unique name defined in Entity Management. Once added, users can select the custom Entity type when adding/editing the Transforms.
The new Entity names can be added on this page:
Note: This page is only used to add the Entity's unique name to the Entity list on the iTDS. Creating the actual Entity definition needs to be done in the Maltego Desktop Client and then added as a paired configuration to the iTDS as well. To learn about creating new Entities in the Maltego Desktop Client, read Create New Entity.