The WML portion of the Builder Xcessory Object Packager offers a way to edit a WML file. But the nature of WML files is such that they can exist in an incomplete state. A widget class, for example, can refer to a superclass that is defined in a different WML file (such as motif.wml).
While editing a WML file describing widgets or components that you wish to make available to the Builder Xcessory when it runs, you may find that you need to load another WML file to make various datatypes, enumeration sets, and constants available to the Builder Xcessory Object Packager. For this reason, the Builder Xcessory Object Packager offers a mechanism to incorporate those WML files without interrupting the work that you are doing on the WML file that you are editing. These "background WML files" can be incorporated by choosing Merge Background File on the WML menu.
Note: Edit screens that are posted are not updated with the new information. You should apply the changes you have made, dismiss the window, and then re-edit the item in order to see the new data defined in the merged WML file.