If you want to edit a placed image, e.g. by sharpening or recoloring the image, you can directly use the Photos.app image editor.
Open image Editor
- Double-click on the image to be edited
- In the image editor, you can postprocess your image
- Apply the processing by clicking on the "Done" button
The picture is automatically updated in the background, maybe it is only after 1-2 sec on the screen to see, you can still continue to work normally.