You can use the commands \AtBeginNote
and \AtEndNote
to modify this behavior.
For normal notes you can add some negative space at the beginning, e.g. \hspace*{-10pt}
, while for the others you have to modify itemize
-specific lengths. For example you can issue a \addtolength\leftmargini{-10pt}
at the beginning and \addtolength\leftmargini{10pt}
at the end so to restore the normal behavior.
In other words, you can add the following lines to achieve what you want
\AtBeginNote{\hspace*{-10pt}\addtolength\leftmargini{-10pt}}
\AtEndNote{\addtolength\leftmargini{10pt}}
MWE:
\documentclass{beamer}
\usepackage{pgfpages}
\setbeamertemplate{note page}[compact]
\setbeameroption{second mode text on second screen=left}
\setbeameroption{show notes on second screen}
\begin{document}
\section{bla}
\begin{frame}{bla}
Some text.
\note[item]{This is a note item}
\note{only text note}
\end{frame}
\AtBeginNote{\hspace*{-10pt}\addtolength\leftmargini{-10pt}}
\AtEndNote{\addtolength\leftmargini{10pt}}
\section{bla}
\begin{frame}{bla}
Some text.
\note[item]{This is a note item}
\note{only text note}
\end{frame}
\end{document}
You can notice the difference in consecutive frames:

Of course, in your document, place those two lines at the beginning.