Creating shortcut in GNOME menu for JGR

 And I am curious if there's a way to create a menu shortcut in GNOME that
can automatically launch JGR?

When you run for the first time library(JGR) in a root R session, JGR
will create a start-up script (here,
/usr/local/lib/R/site-library/JGR/scripts/run). You can then insert
the path into an executable text file (here, /usr/local/bin/JGR) and
use it to create any launcher/shortcut supported by Gnome.
Liviu