The problem is that the .desktop entry for dia is created in /usr/share,
and not in /usr/share/applications
** Changed in: dia (Ubuntu)
Importance: Undecided => Low
Assignee: (unassigned) => Emilio Pozuelo
Status: Unconfirmed => Confirmed
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Installing Dia doesn't create a menu entry
https://launchpad.net/bugs/85596