Extra Spell Menu

My map, Tinker Wars, was nearing the final version when I decided to entirely revamp the spell system. I wanted to add much more customization to the game. In the game Water War - Submerged, when you clicked on a 'learn new ability' button, it was not the standard spell learning menu but an entirely different one with more than 5 spells. Does anyone know how to do this? I would really like the heroes to be able to learn more than 5 abilities. I suppose i could use dialog boxes, but it looked so much more proffessional in Water War.

Triggered, using dummy abilities in a spell book. Heroes cannot have more than 5 hero abilities.