extracted from https://sourceforge.net/p/texstudio/bugs/1933/#4486/b6a1
Example Document:
\documentclass{article}
\usepackage{todonotes}
\newcommand{\glyph}[1]{#1}
\begin{document}
\(x\)\todo{Foo}
\glyph{a} \glyph{a} \glyph{a} \glyph{a} \glyph{a}\todo{x}
\end{document}
leads to 3 + 6 todo notes in the structure tree (instead of 2, see attachment), so the problem seems to be related to backlashes preceding \todo.

I’m using Win7-64 and "TeXstudio 2.11.3 (hg 6281:f89ef8a4cfbd) This is a development version. Using Qt Version 5.6.2, compiled with Qt 5.6.2 R".
Addition: Happens already with 2.11.2
fixed in repository
hg 6288 (0d288bf20747)
hg 6290 (e1d548df682c)
Last edit: Tim Hoffmann 2016-11-13