When both B, C and D are complete, trigger A to run.
In QVP v9 you can currently not set up a trigger for multiple triggers like that:
However, if you can set it up like this in a normal sequential flow:
Or if the jobs B, C and D always completes in a large time difference, for example B always runs very quick, B runs 1h slower and D always runs 3h slower, then you can set up a flow to run B, C and D parallel at the same time, and run A after D. But ofcourse, jobs can be disturbed, and maybe D finishes before B.
So I think a sequential flow will do the thing if it's possible for your time window.