Microsoft Planner has just gained a new copy Task feature, which lets you easily copy tasks to the Plan of your choice. The feature is accessible from clicking the three dots menu on a task, which opens a pop up window where you can change the name of the task, copy it to a different plan and select the task information (progress, dates, etc.) you want to copy.
It’s worth noting that when you copy a task to another Plan, assigngments, attachments, and labels can't be copied across plans. Moreover, the copy task feature isn't available on the Planner iOS and Android apps as of today.
"We'll be exploring and expanding the ways in which you and your team can organize work in Planner, and hope this will be a helpful step forward," said Joanna Parkhurst, Program Manager for Microsoft Planner. You can learn more about this new copy Task feature on the dedicated support page.