Adding inter-project dependencies

You can also show relationships between multiple projects by linking tasks across projects. To set such dependency,  

• Go to your project on which you need to create a dependency.
• Select the Gantt
• Select the task for which you need to add a predecessor and edit it (press e on your keyboard).
• Navigate to the Predecessors tab.
• Click on Add. Under the Project drop-down, select the project and then Task who you wish to set as predecessor for this task.
• Set the Type of dependency and/or the Lead/Lag time.
• Click on Save.

To view dependencies between projects: 

1. Create a report of type 'Task' with output type as 'Gantt'. For steps, refer here.
2. The Gantt part will show you the dependencies as seen in the below screenshot.