Have a look at this thread Footnotes as Sidenotes - #12 by ArloZ - does what you want with a bit of CSS. Has overlap issues if the footnote has a link in it AND text, both otherwise works perfectly. Looks like this for me (I’ve made some style tweaks to match my theme setup - I’m using Minimal):
My snippet file (lightly tweaked from the above thread):
tweak-content-sidenotes.css (1.3 KB)