It took me more than an hour to find out how to drag an image into the textarea. I thought the little handle with the grid-like dots, on the left of the image preview thingi were the way to do it, but no, it is the whole image thingi itself, I have to drag. The grid-like dots are for arranging the the image preview thingies if you have more than just one.
Just in case I am not the only idiot of that kind out there, maybe it would be a good idea to make it more obvious, how to draag images into the textarea for content editors.