Cat-a-lot’s visual file selection (click on a file to select/deselect it) is a really useful way to build a collection of files on Wikimedia Commons and then categorize it accordingly – for example, out of the category for a certain figure skater, select all the images showing them performing a certain figure and then add that figure’s category to all selected files. However, this only works for files within a single category – if the category is broken down (e. g. by year), you can’t use Cat-a-lot anymore. (Or so I am told.)

PetScan can be used to collect all the files within a category, including subcategories, and then export it as a PagePile (another tool that essentially manages lists of files). However, this is missing the visual aspect – it only shows you files by name.

@Harmonia_Amanda requested a way to combine the two – have a way to visually select a subset of a PagePile and then save it as a new PagePile. PagePile has ways to combine or filter piles, but nothing like this. I’m implementing it as a separate tool: PagePile Visual Filter.