I've nailed it hehe :P
Is not that hard If one looks carefully to the Tabs table.... here's what I found ...
Imagine you have a page called "Contactos" (NOTE THE LINK MUST BE //Contactos too... I've noticed in my case the link was //Contacts) and this must be done right because my localized version (en-US) will be named "Contacts" and so the link is //Contacts... we can not ofc have two tabs with the same Path...
So I inserted a new table in SQL most things are auto defined (unique keys)... now here comes the part were you can set any tab "to be" another tab localized version...
1st - Set the culture code column to "en-US" since the original is pt-PT
2nd - Get the "UNIQUE ID" of the primary page.... in this case "Contactos" (pt-PT) this value will be the "DefaultLanguageGuid" in the localized version (en-US) "Contacts"
3rd - The LocalizedVersionGuid (last column) must be equal, so copy the ID from the original page!
Next I did a restart to my DNN application, I could see the new TAB in the EN-US version.... Cool :)
I guess I could also go to "Admin -> Pages" (in the en-US version) add a new pages and then go to SQL and change the values.... This is my next Test actually....
I hope my explanation wasn't much confusing... Perhaps it wouldn't be hard to make some "fix tool" for this but I'll leave that decision to you guys... I can do it in SQL, but others might end up with the same problem!