To activate this script:
- save the script to the folder users > your-username > Library > Workflows > Applications > Folder Actions
- go to the folder that stores your screenshots. Right click to bring up the context menu.
- select Servicess > Folder Action Setup.
- select the script that you save in the first step.
The script will be triggered whenever there's a new item added to the screenshot folder, i.e, whenever you take a new screenshot.
If the Finder is already active, it will be raised to the frontmost, open a new tab, and navigate to the folder containing the screenshot. That way, you don't end up with dozens of Finder windows.