How to export a png sequence with a transparent background from Harmony

I animated a fish jumping out of the water, and I would like to export a png sequence with a transparent background then re import that png sequence as one drawing layer so I can make a particle system consisting of several jumping fish. I did change the drawing type to PNG when clicking on the yellow square to the left of the write module in the node view, but when I did File > Export > Render Write Nodes, then re imported the sequence as one drawing layer, I got a black background instead of a transparent one, even though the original document I animated the fish in doesn’t have a background. Do you know what I can do differently?

Thank you.

Choose PNG4 - The - 4 - stands for Alpha Channel - Transparent Background.

I have found ‘png4’ but I do not see the ‘transparent background option’. Do you know where it is?

It should be enough with selecting PNG4, make sure you don’t have a colour card.