Dear Maintainer,

The desktop file for ImageJ is missing this line (see attached patch):

     StartupWMClass=ij-ImageJ

This is required for the ImageJ icon to be shown in the GNOME 3 dock.
Background information for the curious:

https://specifications.freedesktop.org/desktop-entry/latest/recognized-keys.html#StartupWMClass

https://discussion.fedoraproject.org/t/how-to-ensure-a-launcher-icon-gets-linked-to-the-application-it-launches/67688

https://askubuntu.com/questions/1553339/launch-icon-displays-config-icon-rather-than-specific-icon

https://github.com/flathub/com.google.Chrome/issues/446