Finally, I decided to get to the bottom of this. There are several articles on drag and drop in iOS. For example, you can drag an image from one Note, back to the Notes list and then into another note. Or if you have two apps open at once in Split view, you can drag from one app to another. But what if it's just Apple News that's open? You can still drag images. But where?
After some more searching, I found this article. It's about iOS 11, but the kernel applies to iOS 12 as well. The key is multitouch. (For me, this required using my other hand. As a test, I dragged an image from Apple News to Notes, by way of dragging up to reveal the home row of icons.)
https://www.macworld.com/article/322638 ... works.htmlBut Apple’s implementation goes way beyond that simple Split View drag. iOS 11 really embraces multitouch in a way that previous versions didn’t. While you’re holding that selection with one finger, you can perform other operations with your other fingers. This means you could tap on an app and switch to another view, and then drop the content there. You could even swipe up and into the multitasking view, then swipe to a different app, and tap on that app to bring it forward, and then drop the data.