The goal is simple:
To add a new category structure to articles in Joomla 1.0.15.
All existing category/section should work as it is now.
I have a table with 460 other categories that I want to use to categorise articles not loosing actual category/section structure.
What is imporatant - user/admin should have the possibility to assign multiple categories (those new ones) to articles.
And thats, all, I hope that is easy.