Well, just made a cronjob in Scheduler, and took a look at my crontab file, and it looked like this:
0 0 * * * ls >/dev/null 2>&1 # JOB_ID_1
Notice the JOB_ID_1 at the end.
I went into ~/.gnome/gnome-scheduler, looked at the files there, and there was one named just "1" (as in the number "one") which had a bit of info, including the name
ver=3
title=Hello
desc=
nooutput=1
So, I made a second cronjob:
0 0 * * * ls -al >/dev/null 2>&1 # JOB_ID_2
Copied the file 1 to 2 to match the JOB_ID_2, changed the description, making the file as:
ver=3
title=This is a test
desc=
nooutput=1
Then I switched over to Gnome-Schedule, and it had added the cronjob, and had the name updated.
Follow the same steps, and you should be able to manually name any cronjob you want