Manage multiple plans effortlessly with the new Portfolios feature in Microsoft Planner

You'll see two 'tabs' at the top of the screen next to your Portfolio name: Plans and Roadmaps. Plans is where you add the plan you want to reference and track. Roadmap is where you actually add the detailed tasks from those plans into the view.  After adding the 'Plan' in the Plans tab, it should allow you to 'connect to plan'. Go to the Roadmap view, click on 'Add row item', and the list of tasks in that Plan will show up, allowing you to select which ones to add to the Roadmap view.