Sorry about the luxury problem, but our moodle has 1600 categories. As written in the summary, the categories are not editable anymore over course/index.php, because it takes a browser more then 5 min to display the page, which is more then 2GB after loading. Main reason is, that there are drop-down-menues at every entry, which consist of the entire category tree. So in our case it make 1601 x 1600 entries for the page. It would be better to replace the drop down menue with a button, which opens a menue for choosing the category.

At the moment we help ourself by updating the database directly.