Pixiv artists often present pictures by batch.

This script adds a "Batch Download" buttons that downloads them all in your default directory.

Picture files are automatically named according to their position: "101.jpg", "102.jpg", etc in order.

Make sure to click the "See all" button before you use batch download, so that the images become "clickable" by the script. It will then open them in full view and save them in order. A bit clunky but it works, and you don't even need to stay on the tab.