While having multiple active configurations allows for new objects to apply to all of those configurations, the Schema Editor also supports having a single active configuration but having new objects apply to multiple configurations. One advantage of working against a single configuration but having new objects apply to multiple configurations is that all objects in the active configuration are viewable and editable. Working against multiple configurations only includes those objects that are identical across all configurations.
You can view and manipulate only those objects that are identical across all of the selected configurations when multiple configurations are active. The set of objects that are displayed and manipulated are exactly the same across the set of configurations. Only those objects that are identical are available when working against multiple configurations, which may cause dangling relationships (where the object at the other end is not identical for all of the configurations) or missing relationships (where the relationship only exists in some of the configurations or is different between the configurations). If multiple configurations are made active, it is unlikely that all of the objects for any of the configurations will be available.
Commands such as Validate do not work against multiple configurations because of the dangling relationships and missing objects and relationships. Working against a single configuration but having new objects added to multiple configurations allows all the commands to function.
A potential problem with adding new objects to multiple configurations while working against a single active configuration is that the new objects might cause validation problems for the other non-active configurations. For example, if a new object and a new relationship are created in this environment and the existing object to which that new relationship is related does not exist within all of the configurations then validation of the other configurations generates dangling relationship messages.
However, working against a single configuration while adding new objects to multiple configurations is a useful environment for extending the SmartPlant schema.