Charts: indexed data property is confusing.

What went wrong?

The fact that data is now (as of 4.2) index makes the API a bit confusing. I would recommand that indexes for traces are used exactly the same manner, whether or not data is an array of datasets (used for independent, multi-trace charts) or used as an indexed property:

If

dataset1 = ...
dataset2 = ...
dataset = [dataset1, dataset2]

then <|{dataset}|chart|...|> must be equivalent to <|{dataset1}|chart|data[1]=dataset2|...|>.

Taipy Version

4.2

Additional Context (Optional)

Code of Conduct

• I have checked the existing issues to avoid duplicates.
• I am willing to work on this issue (optional)

✅ Acceptance Criteria

• A reproducible unit test is added.
• Code coverage is at least 90%.
• The bug reporter validated the fix.
• Relevant documentation updates or an issue created in