##Internotes, Not Footnotes!
I grew up with footnotes, and found them flawed on paper. On digital screens, they usually turn into endnotes, which are even worse.
I was tasked with putting a play, originally with footnotes, online, so I took the opportunity to re-think interactive notes for things you read on screen. I tried a side-menu type deal, but ulitmately decided it made the most sense to interweave the notes with the text, since they're really just a form of additional paragraph.
I used CSS transitions to make them speedy, and additional js to make them device-friendly, and copped the classy style from Medium.
Mobile- and device-friendly. There's a toggle to auto-open notes as you scroll, and the notes are able to be hidden if you want to read without distraction.
Not really a plugin, just branched off from the idea behind one.