tl;dr: Like footnotes, but on the side (easy part). These notes must be on the same page as their reference points, so the "main text" needs to break whenever the notes break.

I'm trying to produce something like this:

I've been using memoir . Here's an idea I had. My understanding is that \footnote creates a float that tries to place itself at the bottom of the nearest page. Would it be possible to place the "footnote anchor" elsewhere? For example, with some interesting page geometry, something like this:

The difficult part is in the question title: ensuring that page breaks respect the column-column alignment.

Here is a MWE.