(address . bug-guix@gnu.org)
The icedove.desktop file has no StartupWMClass which makes it behave
strangely with GNOME. If you press Super, search for it, right click and
press "Pin to Dash" it will get pinned, but as soon as you open it, it
will open a new unpinned icon in the Dash, which means, among other
things, that Super + number can't switch to it when it's open.
Adding
StartupWMClass=Icecat
to the desktop file fixes the issue.
Best,
Damiano