StellarNav is just a jQuery plugin for a multi-level drop-down menu; so you may want to Google that to see how to do it yourself; without a plugin.
Way back in the turn of the century, Dynamic Drive was a prime source of menus before JQuery was a thing
Dynamic Drive DHTML Scripts- Chrome CSS Drop Down Menu[
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A List Apart is always a good reference, here's an article on building with JS + CSS:
Suckerfish Dropdowns – A List Apart[
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Then there is Stu Nicholls, who does all sorts of neat stuff with just CSS, like menus
Stu Nicholls | CSS PLAY | CSS only menus[
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