The image manager in the New Drag & Drop Editor, does not allow to search for all the images' names in the root folder. If you are looking for an image included in one of the subfolders (added in the root), then you will need to open the folder and search there. Meaning that from the Root folder, we are not able to search for all images in the Image manager.
The weird thing is that this functionality works for the Drag & Drop Editor. It would be great to include it in the New Drag & Drop Editor.