Things to do first

Close VSCode and save your projects first (obviously).

How to delete WPILib VSCode

Open File Explorer.

On the left side with all of your files, go to the very bottom and you should find "This PC." Click on this and open the Local Disc. Once you are in Local Disc, open the "Users" folder, then open the "Public" folder. It should be right under the folder with your username. In this folder, you should be able to locate a folder titled "WPILib." This is the final location. Find the folder with the year you wish to delete and delete it (duh).

Errors

You will likely get a popup that says something along the lines of the file is still in use elsewhere. To fix this, you can try opening task manager and closing anything that has the words, "code", "Java", "WPILib", or "VSCode". Emphasis on Java, that's probably the problem. Try again once you have gone through this. If this doesn't work, try ChatGPT.