See Before Modifying Dimensional Outlines to identify the changes that may occur if you modify dimensional outlines.
To modify custom dimensional outlines:
On the Object View, select Custom Dimension Setup to display the Dimension Setup page.
Change the structure of the outline by dragging and dropping dimensions and members.
Add or delete dimensions and members. See Creating Custom Dimensional Outlines.
Change the name, description and alias of dimensions and members by selecting them and entering different information in the Properties frame.
Synchronize changes to dimensional structures when prompted. This could include regenerating dimensional measures.