Then, why do you need to create more job for every admin? Creating a configuration for domainsync in your code will help to save time for all WHMCS admins. Do you recognize that? I am not expert in programing, but I guess it will not take more than 30 minutes for adjusting the code. Add an option to General Settings, add functions for saving in database, add a check before running domainsync. Solved.
Don't want to be rude, but you are only speaking from your side, not your customers side and it's not a good practice at all.