I wanted to bring up a later job up in queue to finish it earlier, because the whole queue was working to and from a slow drive.
After GUI collapsed, Task-Manager says mkvmerge.exe is still running
and disappeared after current job was finished.
When re-opening GUI, job queue is beginning to start the next job in queue automatically and showing last job to be failed. Order did not change, but the queue worked from then just fine.
It would be nice to be able to change the order of jobs while the job queue is being processed.