When editing any 'Event Combination' belonging to either a SysCon or an OpEnv, it is mandatory to choose ANY ONE of "Chagne OpEnv/SysCon" OR "Queue Table", otherwise the event combination cannot be created.

It makes sense that we have to provide the "Change OpEnv/SysCon" field for a combination because without it the event combination remains dangling.
But the other option of selecting "Queue Table" is also allowed when an event combination is created. No OpEnv/SysCon will be effected by this so does it make sense as a valid option?

The only explanation I can think of is that by enabling the "Queue Table" only we can monitor in the SystemQTbl and analyze if we need to map a OpEnv/SysCon over this period combination. Would you agree?