Add Categories
Steps
Click Assignments and select Gantt (Beta).
Next to the project name, click the vertical ellipsis
and select Add Category.To add a subcategory, click the vertical ellipsis
next to the category, and select Add Subcategory.
OR
Right click the category bar and select New Subcategory.Enter the name of the subcategory.
Click out of the text box to save.
Tip
Click the undo 
icon to undo an action. Click the redo 
icon redo a previously undone action.