Saving MAC screenshot to Photos

After you take the screenshot as described in (How to take a screenshot on your Mac - Apple Support), you just drag it to the Photos icon in the Dock. Photos will import it. In Phots, drag the screenshot to the album, where you want to collect your screenshots.

You can automate this procedure, if you change the default folder, where screenshot are stored. Create a special folder and make it the default folder for screenshots, as described here: :How to Change Screenshot Save Location

Then add a folder action script to this folder, that will automatically import any items you add to this folder to your Photos Library. This is described here: Automator Service for an Auto Import Folder for Photos

You can not - screen shots save to your local disk - if you want them in iPhoto (or Photos either) then you have to import them

And in iPhoto or Photos folders do not hold photos, folder hold albums or other folders - photos are in events (or moments)

LN

https://support.apple.com/en-us/HT201361

Hopes it can help you.