A very short post to help other people that might run into the problem of finding the holy grail: a responsive, multilevel menu built with Bootstrap3.
Bootstrap 3 removed support for multilevel dropdowns, citing usability issues as the cause. I argue that there is a use case for multilevel menus when used sparingly and responsively. In a recent project I built with bootstrap, I found myself needing a 2 level main menu. I had assumed that Bootstrap could do this- after all its advantage is its ability to take anything you throw at it.
When I finally found the answer I was skeptical at first:
Smartmenus is a jquery plugin to create responsive multilevel menus. I had considered using a standalone responsive menu script, but it seemed like a nightmare to integrate it with bootstrap styles and functionality. However, smartmenus has a plugin designed to work specifically with Bootstrap, and to respect all the bootstrap styles you have defined; it just extends the functionality! You can have navigations with multiple levels, and it automatically works on hover for large screens and on click when collapsed.