when exporting png / transparent images, the optional feature is needed, auto crop image to the edge of real - visible image.
(Illustrator common feature)
What features would you like to see in Pixelmator Pro?
Are these multi-layered images by any chance? If they are, Add for Export feature might do the trick. It lets you add individual layers for export, so if, say, you have two layers — a background layer and a shape/image layer, you can use Add for Export to export just the shape or just the background.