Comment by mort96

You don't need to bloat any menu. There's already a "Save image as..." context menu option which opens a save dialog. This dialog could have a way to select format.

I just tried it out now, using Waterfox on macOS 27. The save image dialog literally already has a Format dropdown. But I'm guessing it's just a weird part of some native dialog, it lets me select between "WebP Image" and "All Files". This kind of design could've been used to allow the user to save it as a different format than what it was served as.