I tested a few things, such as the autocomplete for p5-specific functions and the warnings triggered when functions like setup or draw are used in undesired places. They work well.
The Jump to Definition feature also works fine. I tested it across multiple files, and it correctly jumps to the function declaration in another file when the function is called from there. When multiple functions with the same name exist in different files, it follows the runtime behavior. However, instead of just moving the cursor to the function declaration, it would look visually better if the function name were briefly highlighted, for example:

But the functionality works well.

The context-aware renaming feature works with Fn + F2 on some systems. I tested it with variable scopes:

function setup() {
  createCanvas(400, 400);
}

var x = 10; 

function draw() {
  var x = 10; // local variable (shadows global x)
  background(220);
  x = 20;     // modifies only the local x
}

I tested context-aware renaming and it works for functions within the same file.
However, when I rename a function in sketch.js that is defined in another file, the function definition in that other file is not renamed.
Example:
sketch.js

function setup() {
  createCanvas(400, 400);
}

function draw() {
  background(220);
  hello(); // call
}

hi.js

function hello() { // definition
  console.log("Hello");
}

Renaming hello() in sketch.js does not update the function definition in hello.js.
Is this the intended behavior?

Regarding context-aware renaming, yes, that’s the expected behavior. From what I’ve seen in most code editors, the renaming only works within a single file. It won’t rename the same function or variable if it’s defined in another file. It would also make the browser editor's functionality more complicated so I thought it would be best to not include such a feature.

Thank you for your feedback and all your suggestions! I'll also try to add the jump to definition highlight feature.

Thanks so much for your work on this @kammeows!

I think this looks really great so far, and I really love how much smoother this overall looks! I don't think I have too much to add on to @diyaayay's comments, and I feel that they covered most of my initial thoughts while testing out the feature!

I do have a quick question—while loading this branch, I ran into a small version mismatch issue between eslint and eslint-plugin-storybook, which I resolved by changing these versions. I was wondering, was this something that you faced as well?

Hey @raclim! Thank you for taking a look on this. No I did not encounter any such issue. If it comes up again, we can look into whether we need to adjust the package versions in the repo to prevent others from hitting the same issue.