EViews.com

I noticed that if an add-in gets reinstalled or happens to be part of a package installed later, EViews would create TWO stances of the add-in in the add-in menu.
I hope that get corrected in a way that allows no duplicates.

I don't believe this is true. Upon re-installing an Add-in, EViews will prompt you, asking if you want to install on-top of the existing Add-in, and the Menu items will be replaced, not replicated.

Maybe that is limited to the (Normtest) add-in, because when I installed them first (they where separate files) they were located in the mother add-ins folder, but when the package Normtest is installed EViews created a folder for that package inside the add-ins folder; in EViews menu there were two instances of the application names.

Even if EViews asked to confirm installing over a previous installation, it shouldn't be allowed to have two add-ins under the exact same name, that is my main point.

But we want to allow Add-ins with the same "name". Remember an Add-in is not really defined by its name. An Add-in is a file on disk.

It could be that that file on disk works on both series and group objects. Thus you could have an entry in the Add-ins registry for two instances of that file, both with exactly the same proc-name, both with exactly the same menu text. One is works on groups, the other on series though.

It could be that the Add-in does two different things, thus it may be that the exact same Add-in has two different proc names, even though they do exactly the same thing.

As you can see, we've allowed a lot of flexibility, with the idea being that we've (hopefully) given the user a nice enough interface for Add-in management, that they can sort out any potential problems themselves.