NewPlanner
Planner: Track task progress with the Completion (%) field
Planner users will gain a new Completion (%) column to track task progress as percentages instead of binary completion status. This provides more granular visibility into incremental work progress and team task status.
Microsoft's description
The new Completion (%) column in Microsoft Planner provides a more precise view of task progress. Users can view and update completion as a percentage, helping teams communicate incremental progress and quickly understand how far work has advanced.