Answering my own question.
The blue drop is a button. Pressing it will cause the dose to dispense. It appears to work like the physical manual button on the doser. Press it briefly and it operates briefly. Hold it down and it will dispense for the time it is held down.
It was scary for a while, because I am not at home and was unsure what was happening when I originally 1st pressed the blue drop button.
So I set up dose pump 4 through the app and messed about with. Pump 4 is spare for me. I can relax now.