As seen on page 200 of pgf manual is there a way to put notes in the margin but on the same level as the place it is called ?
One can deal with the right-left positionning with the help of this question margin notes multicolumn, but how to deal with up-down level ?
Edit
With your help, here is my try. Still vertical alignement problem.
\documentclass[french]{article}
\usepackage[marginparsep=3pt, top=2cm, bottom=1.5cm, left=1.5cm, right=1.5cm]{geometry}
\setlength{\parindent}{0pt}
\setlength{\headsep}{1em}
\usepackage{tikz,lipsum}
\usepackage{multicol,zref-savepos}
\def\Note#1{%
\zsavepos{#1}%
%%%%%%--------
\ifnum20000000<\number\zposx{#1}%
\begin{tikzpicture}[remember picture,overlay]
\coordinate (here) at (0,0);
\draw (current page.east |- here)
node[left]{\makebox[1.2cm][l]{#1}};
\end{tikzpicture}%to prevent adding extra space before text
\else
\begin{tikzpicture}[remember picture,overlay]
\coordinate (here) at (0,0);
\draw (current page.west |- here)
node[right]{\makebox[1.2cm][r]{#1}};
\end{tikzpicture}%to prevent adding extra space before text
\fi%
\ignorespaces
}
\begin{document}
\begin{multicols}{2}
\lipsum[1]
Un essai de note dans la colonne de gauche.\hfill\Note{1pt}
\lipsum[2-3]
\Note{1.5pt} Un essai de note dans la colonne de droite.
\lipsum[4-5]
\end{multicols}
\end{document}