Hello! Picking a category for this question was a little awkward since 1. I'm 99% sure this mod doesn't exist so it's not a WCIF and 2. I'm not a modder, so I don't intend on creating it
I was wondering if anyone with script mod experience could answer: is it theoretically possible to create a UI mod that organizes clothing swatches under a single icon, like in TS4? Or are there limitations in the engine that would make this impractical?
I love TS2 but one of the most tedious things about CAS is scrolling through pages of color variations for the same item of clothing. Thanks to anyone that can answer!

I doubt it, as that's something that would need to be based on what's in the game already (reasonably sure it's a core function). Objects have a swatch system, but they're also sorted very different than CAS items are.

The closest you get is to use the "SortIndex" number in the Binary Index to move items so they sort together (unfortunately doesn't work in the wardrobe, but does work fine in other menus + CAS/Bodyshop).

There's also the BSOK system, but that's mostly used for body shape clothes: https://www.picknmixmods.com/Sims2/...BsokEditor.html
(It allows for clothes to sort together, and is based mostly on how non-CC clothes have custom icons, using strings/resources that are already available).

If you have a lot of recolors of similar items, and you find you hardly use most of them, maybe it's time to clean up a bit in your CC and remove stuff you don't use. It's also a good idea to be a bit more critical when you put stuff into the Downloads folder - if there are colors/patterns you don't like, or they're too similar, or you're unsure if you'll use them, or you test out the items and find you don't like the item in general, it's better to not put them in - or take them out after testing (I've taken to test items out in Bodyshop and/or a test game - previews don't always give you a good look of the item).