To me it looks like you can add two excell addins to an Office environment. 
You can create an excell file for the TEST env and another one for the PROD env.

(Note that you have to download the manifest for both environments then, TEST and PROD)

Then you can just copy paste the data from one excell file to another.

Note that you cannot export Excell migration jobs so you have to recreate the job in the PROD env

and grant the needed access to the excell migration projection. 

Thanks,

While waiting for this answer I found out the above myself too.
But, it is possible to export/import. You just need to grant your user access to the FNDMIG_EXPORT and FNDMIG_IMPORT jobs.

And another thing that I also found out. Both jobs (test and prod) will have the same name in Excel so it is difficult to tell one from the other.
Before you add the Add-In into Excel you can edit the XML file and rename the add-in label that is visible in Excel.

Thats a very good suggestion! 

That should actually  be a feature request. That the Excel migration tool should be named with an indication for the platform you are on.

Agree to that.
Just add a field in the ‘Generate Excel manifest’ where user can give the plug in a unique name that will be visible in Excel.