@Andrés,

It is possible through the backend by going to Settings >> Website Settings > Configure website menus.

When I can find a bit of time I plan to build a frontend interface for this that handles category trees beyond the current limitations to the frontend interface out of the box.

I recommend building your category tree from the backend, as you can build unlimited subcategories.

@Luke Thanks for your fast answer. I have tried what you've said, and I have changed just the "Parent menu" field, but it doesn't work correctly: - I can see now that "Option 1.1" has an arrow (which denotes that it has a submenu). - If I click on "Option 1.1", it doesn't open the submenu, nor goes to the "Option 1.1" page I've seen that if I edit the menu from the "Website Settings", I have an icon next to the parent menu which allows me to modify several things, but I don't know what do I have to modify. Is there some manual which explains this? Thanks.

Andrés, it works just like Luke said, you have just to add another submenu to be able to view it correctly, I don't know why, maybe it needs two or more submenus to be recognized, it's not working properly, but at least it giving a result.

Andrès, it's not working properly at all, I've tested it again, and it's working for one item, and it should have imperatively a second menu beside, otherwise it doesn't work. So it's a complete mess, that's it. I'm correcting my self, I hope we get a proper solution for this.