Hi @rashmikamudalinayake10,
unfortunately, the Add Item dialog is not customizable, because it uses a legacy approach of logic generalization -- it is a descendant of PXSelectBase, and they are not customizable at all. You could try to create a descendant of the SOSiteStatusLookup<Status, StatusFilter> class, and replace the original view with it (by creating a graph extension that contains a new class as a view with the exact name, that is used in SOOrderEntry -- sitestatus, and probably override these two actions: AddInvBySite and AddInvSelBySite). However, since this class have a very small amount of virtual members, this might not help the situation.
Acumatica have plans to refactor this functionality and move it to a graph extension approach, what would simplify the customization drastically. Please report a support request for such a change, if you would like to have an ability to customize that dialog easily.