Use case: I'd like to write a two-sided document, with prose on the RHS and sidenotes on the LHS, with (if possible) the note appearing parallel aligned with its label in the prose.
I can do this with the paracols package, with all the text on one page. But I don't know how to lay it out across two pages.
Approximate MWE:
\documentclass[a4paper]{article}
\usepackage[landscape]{geometry}
\usepackage{paracol}
\usepackage{lipsum}
\begin{document}
\begin{paracol}{2}
\switchcolumn
\lipsum[1]
\switchcolumn*
\textbf{prose}: The long and boring part of a document.
\switchcolumn
This constitutes a long and verbose set of \textbf{prose}.
\switchcolumn*
\switchcolumn
\lipsum[1]
\switchcolumn*
\switchcolumn
\end{paracol}
\end{document}
So, as you can see, for each reference on the recto page (at the moment just regular bold text), I'd like to add details on the corresponding line on the verso page. Is there a way to refer to the "corresponding line on the opposite page"? There are various edge cases like "what if you have two references on the same line" or "what if it doesn't fit on the page" but I imagine these are not hard to deal with.