Step 1: Click on the timeline object you want to manually change
In this example, we will manually change a date. Select the date you and manually type in the change you want to make. This can be a date change, or formatting changes you would like to make to any object.
Step 2: Click Accept Manual Changes
From the office Timeline Ribbon in PowerPoint click Accept to save manual changes you have made to any of the objects or text on your timeline.
This video show to save manual changes
See these quick videos for more tips: