Improve warning and documentation for built-in scripts in the Attach Node Script dialog

[ghost]

Describe the project you are working on

Any project where user might want to use built-in script.

Describe the problem or limitation you are having in your project

Script creation dialogue doesn't bring much specifics about "Built-in scripts".
It only says "Note: Built-in scripts have some limitations and can't be edited using external editor." and "Built-in script (into scene file)":

First

What does "some limitations" mean? What kind of limitations?
And what exactly "Built-in script (into scene file)" means? It will be stored as text in scene so like zip archive? Or "inside" node? Where exactly?

Searching for "godot built-in script" doesn't bring much in google, with exception of like 2 reddit posts and some Godot questions from Godot forums https://forum.godotengine.org/t/what-is-a-built-in-script/31691/4 and also there not much info in docs. Even "Your first script" (https://docs.godotengine.org/en/latest/getting_started/step_by_step/scripting_first_script.html) omits this part as not important: "Leave the other options set to their default values and click the Create button to create the script."

So, alright, after some googling I know that if I remove node with built-in script, script apparently will be lost (so it wouldn't be stored as script inside zip archive rather, so I can't reuse it simply as external script which explains why file can't be edited using external editors).

What about other limitations? Is there more of them?

Second

Why even use built-in script? Why user might want to prefer it over external script? What benefits and downsides? (Without knowing all possible limitations it might not be easy to decide this).

Describe the feature / enhancement and how it helps to overcome the problem or limitation

Documentation for this feature should make it easier for users to decide if using built-in scripts worth it and if limitations will affect them.

Describe how your proposal will work, with code, pseudo-code, mock-ups, and/or diagrams

There should be documentation for built-in scripts (or, if it already exist and I failed to search for it, better discoverability).

And script creation dialogue should have link or button to open documentation about built-in scripts:

If this enhancement will not be used often, can it be worked around with a few lines of script?

User could look for answer using Google and browsing Godot subreddit and forums, but that doesn't sound that good for built-in feature and for users who might not have internet.

Is there a reason why this should be core and not an add-on in the asset library?

This will improve core Godot experience, especially for newer users who might not have any clue how this even works. Also, considering this proposal: #1274 there was even debates about it and how it should work, even suggestions about removing (or explaining better what kind of limitations user will face) this feature: godotengine/godot#31758. There also was comment about adding current hint: godotengine/godot#31758 (comment), but still no docs.