Answering to myself in case you are interested. You most likely need a Pinterest account for this.
Go to https://developers.pinterest.com/tools/widget-builder/? and configure the Widget Builder as follows:
- For Button Type choose “Image Hover”
- Click “Large” (makes more sense for me to make it visible)
- If you just want the Pinterest P in a circular button, also click “Round”
- When you are not using “Round”, leave Language on Default Setting except if you want to enforce a language of the text “Save” in the pin.
You can then see a code snippet with a script tag on the right hand side of the page. Copy this into a basic HTML stack for example and put it on the page. I have put it before the gallery stack. All your pictures, independent of looking at them on the page directly or in Lightbox mode, will show the P button in the top left corner of the image when you hover over it. The button is picking up that specific image as Pin for Pinterest and links it to the page this image is on.