Hello,
There isn’t exactly a way to do this however you could simulate this by changing the g_intSoftwareDistributionSimultaneousJobsLimit from 5 to 1 in the ConfigMgr Global variables screen within the QMX Administration Console. This would allow only one job to run globally at a time which would get you the behavior that you want. It does mean that QMX will process only 1 install at a time though.
Once the above is done you will need to stop and start the software distribution process for QMX. This can be done by going to "Tools" -> "Services" -> "Software Distribution", click "Stop", then click "Start".
Thanks,
Jeremy Thompson
QMX Support