Linux Firefox Developers Edition - Stacked taskbar icon (So that opened windows stack under the actual launcher icon when favorited)

firefoxdeveloperedition.desktop

# In /usr/share/applications/ create a file named 'firefoxdeveloperedition.desktop' and put the following in it (If you installed it somewhere other than /opt/firefox/firefox - change the line Exec=/opt/firefox/firefox to reflect this change)

[Desktop Entry]
Version=1.0
Name=Firefox Developer Edition
Comment=Browse the World Wide Web
GenericName=Web Browser
Keywords=Internet;WWW;Browser;Web;Explorer
Exec=/opt/firefox/firefox
Terminal=false
X-MultipleArgs=false
Type=Application
Icon=/opt/firefox/browser/chrome/icons/default/default128.png
Categories=GNOME;GTK;Network;WebBrowser;
MimeType=text/html;text/xml;application/xhtml+xml;application/xml;application/rss+xml;application/rdf+xml;image/gif;image/jpeg;image/png;x-scheme-handler/http;x-scheme-handler/https;x-scheme-handler/ftp;x-scheme-handler/chrome;video/webm;application/x-xpinstall;
StartupNotify=true
Actions=new-window;new-private-window;

[Desktop Action new-window]
Name=Open a New Window
Exec=/opt/firefox/firefox -new-window

[Desktop Action new-private-window]
Name=Open a New Private Window
Exec=/opt/firefox/firefox -private-window