Direct manipulation of data points on charts
You can drag data points on a chart and change their source values on the worksheet.
Dragging data points to change the source values on the worksheet is no longer supported.
Source of information:
And what does this have to do with Libreoffice?
So to have a correct explanation of this feature request:
The idea is to be able to allow modifying the value of data point directly in the chart.
I see several problems on the way to this feature. The current design with data providers and data source hides the relationship between data point and data. Additionally this is a bit of a nightmare when ti comes to cells that are the result of a calculation and not pure values.
I suspect that the Excel team removed this feature for the second reason.
We would have the least problems with the internal data provider but I suspect nearly nobody is using the internal data provider as long as the chart has not been copied.