In case you want to invoke job scheduler then I think it is still the best way put it to some /home/ directory and attach job to cron. Just attach it there via WebUI or CLI commands:
HostName> set cron job JOB_NAME command ...
HostName> set cron job JOB_NAME recurrence ...
In that case job stay to be scheduled in your configuration file. On the other hand you must still have the script itself backuped somewhere.
For me personally it is not a bafd enchancement to have possibility to use Script repository and just schedule same script for example on different firewalls throuh console...