3450068 - How to update the duration of the Project Phase when the duration of the respective Project Task is modified?

Duration of the Phase in a Project cannot be edited when the duration of the Task is modified

SAP Business ByDesign 

Once you change the duration of the Project task, kindly follow the below steps to update the duration of the subsequent Project Phase.

1. Go to Project Management work center 
2. Go to Projects view and search for respective Project ID ABC
3. Select the Project Plan tab
4. Go to Gantt chart sub tab and click on More(>>) and then Options
5. Select the Schedule tab. This will automatically schedule the Phase duration based on the Task duration. 

Kindly refer to the below blog on Project scheduling and its aspects for further information. 

Project Scheduling | SAP Help Portal

Project Phase duration update, Schedule the phase duration, phase duration  , KBA , SRD-PRO-PMN , Project Management , How To