Hi Nicole,
Let me make sure of your problem. Do you mean the added images won't show up in the workspace when you reimport the JSON data which is exported using PhotoshopToSpine? If so, note a point that the JSON will only write about the images that were exported at the same time. For example, if there is an image that is excluded from export because the layer is hidden, the information about that image will not be written into the JSON.
If the problem is that you can not find the added images in the Images node as you've posted a screenshot, then I guess you have too many images in the same folder, which limits the scan. By default, only the first 2,000 image files found in the image folder are shown. Uncheck Limit scanning
to allow Spine to find more than 2,000 image files.