XDP removing PNG transparency when I open/edit/save direct. How to keep transparency?

[handrawn]

it's my understanding that when editing photos directly, as opposed to importing them into a document, it will always default to true colour saves unless you tell it otherwise - this is the only way I know to tell it otherwise... [it does not default to the export dialog box, and the settings button is easy to miss]

I don't think the problem is in the external bitmap editor transfer proccess - but I could be mis-reading it...