What you need is API QUSLJOB. Format JOBL0100 is enough for what you want.
It will list all jobs for a specific name and you can filter *ACTIVE only.
Thank you for the answer. I had actually looked at this API but read it wrong – I thought it required me to know the job name, user name and job number in advance. I’ve now taken a second, closer look and see that I can give *ALL for both user name and job number and since only one job (of the job name) should be active at any given time, I can then extract the active user name and job number.