Intervals is designed in a fashion that does not include traditional task dependencies like the waterfall method and MS Project utilizes (Finish to Finish, Start to Start, lag, lead, etc.) and is built more around Agile project management philosophies where tasks are more free form in nature and milestones are utilized heavily.
The closest functionality to task dependencies within Intervals is milestones. The milestones piece does have quasi dependencies if you need to shuffle your project around. Say for example there is a design milestone that ends the first phase of a project and it runs late. You can move the due date of the first milestone and all of the other milestones and tasks will move as well. More information about rescheduling milestones is available in this article. If you haven’t used milestones, this introduction and video might be worth a look.
If you are interested in seeing each project and the milestones in a Gantt chart like display, the Periscope report might be helpful too. Here is an introduction to the Periscope report.