A Basic concept to tell but getting a lot of queries on Compossite forms global dimension.
In Hyperion Planning Composite Data Form page Dimensions are not shown as Global Dimensions.
This is due to Different members of the same dimension have been selected in both forms, creating the composite form. If we select different members of same dimension in the simple forms, composite form will not shown them as Global Dimension in the Page section.
Edit the Simple forms used in the Composite form and make sure to Select the same members in both forms of the Page Selection.