I don't know of any modules that do multiple rows of tabs in Tk. Since a NoteBook page is just a frame, there is no reason that you could not put another NoteBook inside that frame. It would not look quite right, as notebook tabs on both rows would be enabled, but if the tabs could be arrangd hierarchically, then it would be fine. The first row of tabs would be broad categories and the second row would be specializations of those broad categories.

From a UI point of view, too many tabs, like you see in some Windows dialogs, make my eyes cross :) At some point, I think it would be better to go with with ListBox of categories, where clicking on a category brings up the associated dialog.

You might also consider Tk::DynaTabFrame as an alternative. The widget takes care of too many tabs by stacking them and having left/right arrows to scroll through them, similar to the worksheet tab interface in Excel.