In at least the Categories and Assets apps (maybe others as well) user will expect to see the created item - therefore if creating an item in a closed folder (or any kind of parent) the folder (parent) must be automatically opened on creation.

Probably the solution is to emulate the event fired as in OpenCreateDialogAction:
eventBus.fireEvent(new ContentChangedEvent(item.getWorkspace(), item.getItemId(), true));

...in the action responsible for creating categories and assets:
CreateItemAction.

mplementor should also check the other main apps to ensure that the behaviour is correct there as well.