Hello, everyone! I believe this is my first post here, but I would like some help with something. I've spent the past few days trying to figure out how to go about making a mod that allows you to remove all parts of a clothing category with a button, like how the makeup section has that X button that you can click to remove every instance of a category. For example, if I want to take off a Sim's top but can't find it in CAS, I can have that same X button pinned to the first row of the top category, or if that's too complicated to code, just right-click the top icon or something.

I haven't seen any mod that gives that kind of functionality, but it seemed rather simple to me, so I figured I could do it myself (I have experience with C#, but this would be my first script mod ever). However, the more I look into it and examine so much decompiled code, the more I feel discouraged. Is this idea just too ambitious or not possible due to limitations, or am I missing something? I'm not necessarily looking for a complete walkthrough or anything, of course; perhaps just a nudge in the right direction. Thank you so much and have a great day!

Welcome

The limitation here is that sims don't equip clothes, they are their clothes.
Clothing meshes include the arms, hands, ankles, so on. A sim that removed their top would be invisible from the neck down to the waist.

If you just want the functionality to quickly switch to the nude top or bottom, that's actually possible without any scripting.
These exist as CAS Parts like any other clothing, they're just hidden (except the nude male top and the bare feet).

You can use the software S3OC to clone the nude CAS Parts. They are named like 'afTopNude', 'afBottomNude', 'afShoesNude', so on for each age and gender.
You can set the categories in the left panel before you clone - tick every category you want, and make sure to untick ValidForRandom.

Then open the cloned package in S3PE, click on the CASP and click the Grid button in the bottom panel.
In the SortPriority entry, enter the number 9999. Higher number = the item will appear higher in the list of CAS. This will act as the 'lock to the first row' part.
Repeat for each part, then drop the packages in your Mods folder and they will be the first option in every category.
You could even give them custom thumbnails with the X, if you'd like.

CardinalsSims' solution is probably the easiest and most hassle-free solution you can get away with. But if for whatever reason you prefer to make your own mod for that, this is how I'd go about it. However a small disclaimer first: I've never made a mod like this, it's just that I like looking into the game files and occasionally playing around with them when I get an idea for something new to make. Hopefully, I'm not blatantly wrong.

This type of mod would probably require two parts, one that's coding the script itself and another one that would involve modifying the UI. The latter should be the easiest, because, as far as I know (and please someone correct me if I'm wrong) the UI is controlled by a bunch of CSS files inside the UI.package that can be found in the bin folder inside a subfolder named "UI". You should open it with S3PE and find out which CSS resource controls the CAS UI. You can add a button by examining other CSS files to figure out the exact syntax. Once you've written code that works, that is, the button appears in game and is clickable, you'd need to make the script for it, because without it would just do nothing.

Now, as CardinalSims said, you can't just remove clothes from a sim because the clothes don't just "sit" over the body of a sim like in real life, they include the shape of the body that they cover (or reveal, and please correct me if I'm not using the correct terminology). Because of that, you'd have to make a script that changes the sim's clothes to specific CAS parts. Normally, you'd want to go for base game underwear as bottoms and a nude top for male sims or matching bra for female sims (this could be made tunable for more flexibility). That would give the illusion of the sim undressing. I'm no coder but I have the impression this type of script shouldn't be too complicated to code. Hopefully someone else will know how you can assign the script to a custom button.

Not sure of your age, but there are naughty mods that "remove garments" and replace with nude parts. So, it is definitely in the coding.

Thank you for the quick replies! So basically, I just have to make a clone of the base game underwear and set it to high priority with a custom thumbnail. I don't know why I didn't think of that lol. Thank y'all for the help (and don't worry, I am an adult !)