'Cross-Project Relationships' allow for entities in one project to be related to entities in other projects. 

1. Enter 'Entity View' on the entity you want to relate to and click the dropdown arrow next to 'Add' on the relationship you want to use to relate the two entities and then click 'Relate Existing Entities'.

2. Click the gear button next to the entity dropdown menu and then expand the 'Projects' section by clicking on it.

3. Locate the project you wish to relate the current entity to either by clicking on it in the list or searching for it the input and then clicking the project name in the search results. You may need to increase the search limit by clicking '30 entities' or '50 entities' if you can't find the entity you're looking for.

4. Click the entities you want to relate to in the dropdown menu. 

5. Either click the green checkmark above the gear icon or de-click anywhere else on the screen to finish adding the cross-project relationships.

6. Your newly added cross-project relationships will now show up in the 'Relationship Sidebar'. Click the green 'Save' button to persist the changes to the database.