Photonium Access allows you to access your entire Photos.app library whenever you need it. Just click the Photonium Access menubar widget to display your Photos.app library. Make the thumbnails bigger or smaller. View by folder. You can even preview video files. When you find the image or video you want, drag and drop it into whatever application you want it in: Pages, Keynote, Word, PowerPoint, Safari, Affinity Designer, Creative Suite, and any application that accepts drag and drop.
Note: Now requires OS X 10.15 or later