Editing Domestic Cup via "Add to existing Structure"

Hi,

I've created a lot of teams in Slovakia to create the 3rd level. I guess I can do that simply by choosing "add" instead of "rebuild from scratch". Now I'd like to edit the implemented national cup in such way that there is one more round, which would be a bit closer to reality. But changes will not be accepted, even if I go and delete the whole cup altogether it will still be there in the game.

That means, if I wanted to change anything in the "existing structure" I'd have to rebuild everything? Or am I missing out on something?

Edit: Nevermind, I've found out myself. Had to choose "overwrite rules", that's all. Works now.