The Save/Export split still catches me out. I'm not about to burn the barn down, but each time it makes me grunt in frustration.
Practically every image editor on the planet split saving in the application's native file format and exporting to foreign file formats.
Hell, even document editors do this.
The expected workflow is, therefore, that exporting is a different dialogue. Not terribly hard.
I do not have many editors installed here, but Paint does have all formats on Save. Paint Shop Pro also has all formats on Save. I do not have it installed, from what i can see in the documentation[0] Paint.Net also has all formats on Save. LazPaint also has all formats on Save.
I'm sure i can find many others if look for (i think GraphicsGale for example also does that but i'm not 100% sure). Those are from the top of my head.
Maybe with "Practically every image editor" you really meant "Photoshop"? Because Photoshop isn't the be all end all of all image editors nor all image editors are meant to be Photoshop clones.