As I remember and from what I see in the code, it doesn’t matter if an image was added using toolbar or using drag-and-drop. In both cases, this should work.
Also, I tested it and looks like now everything works as expected (it’s hard to tell when exactly this was fixed, but I think it’s not so important). Here are videos for drag-and-drop, but it also works when using toolbar.
In the middle of the line:
At the end of the line:
At the end of the last line: