We have EM12C and among several other things we use it to schedule backups and other jobs on our several Oracle databases.
My question: Is there a way to manually execute a scheduled job, a sort of "execute job now" type of command
I'm not sure how you're doing the jobs? The same jobs you schedule in EM job system you should be able to submit anytime.
I opened an SR with Oracle and they confirmed that there is no option to "execute Now" a scheduled job on EM12C.
What can be done is to edit the job schedule to run in say next minute and then re-schedule it again to normal time.