Yes there is.
It's in /snap/gimp/current/usr/share/applications/gimp.desktop
It also works to copy that to /usr/share/applications or maybe a symlink will do.
This will require editng the Icon=path in that file,though.
The adding and editing thingy is a nice simple stanza to add other personal stuff to the dock ....... like a lockscreen or a screen-rotater icon for on my tablet.
