How can you tell if a call is a parent or child call from the workload list

You could put a calculation on the individual process objects (I, P, R etc) which counts the number of child processes and display this, but you will not be able to access those from the process level query.  The objects that support the link to child are just not there. 

Could you so something like add a boolean to the form itself then in the process when you choose to add a child have it set this "is child" flag?  then you could write a query to show which of these are true or just add that column to an existing query.  Just a thought of the top of my head.

The brains trusts gathers ... :-)  I think the problem there is that you can 'wrap' the attach child action with your own and then add setting an attribute afterwards, but if you detach a child you need to do much the same in reverse.  For that I've found it hard to wrap the detach child action.  I think I got it to use a new windowless action telling you to detach, then you ahd ti manually run the real detach action allowing you to select, then you could hook i nyour own automatic action.  It meant double keying on that action each time.  Do-able, but not elegant.

Did somebody say 'trigger'?

I see what you mean.  A trigger could work well.  Enhancement Request?