How to create another (secondary) dashboard inside the tab of the main/primary project dashboard?
Accepted answer
Dashboards are not nested. Presently dashboards can be at Project Area, Team Area or User's personal dashboard. However, a user can create multiple dashboards and a dashboard can have multiple tabs.
So, you can have a project dashboard with a simple Headlines widget which contains the links to other dashboards you have created.
Visit https://<server>:<port>/jts/dashboards/all to see the existing dashboards and create new ones. Of course, you should have required permissions to do so.