Feature request: Add annotation(s) into the legend

[HuongSakada]

For Chartjs, we can create the chart with the legend and can show or hide it by selecting the legend.
Do we have any ways to add the annotation into the legend?

[stockiNail]

@HuongSakada my personal opinion, that's not possible because legend items are representing a dataset or data of dataset. In this case you would like to have a legend item to a chart element.

I guess (but correct me if I'm wrong), you want to have the possibility to show and hide the annotation on demand.
If you are using the last pre-release v1.0.0-beta.2, this is possible by display options and of course an external HTML "controller" which can enable or disable the display of the label.

[HuongSakada]

Yes, you are right. If we want to show the legend it must be added in datasets.
So I have a trick, add it as data in datasets of type: 'line' with data: []. I don't think a good solution but it can help.

{
    type: 'line',
    label: 'The legend label',
    backgroundColor: 'red',
    data: []
}

[LeeLenaleee]

If you really want a label in your legend without adding an extra dataset as posted as a solution you can also define your own generateLabels function that returns the label items for all datasets and one extra for your custom informative label