Data point labels and ChartDataCaption: Explanations needed

The API documentation describes a constant group
com::sun::star::chart::ChartDataCaption Constant Group
It’s purpose is explained by
“These values specify how the captions of data points are displayed.”.
The constant CUSTOM (=32; since LibO 7.1) is explained by
“The caption contains a custom text, which belongs to a data point label.”
Who’s in the know and can tell me where that custom text per data point lable is taken from?
An .ods containing a chart (and probably related user code) clarifying how data-point-captions (and the mentioned constant) are used would be very welcome. I found no clue.


Why do you think my question might be related to that old bug?
What I tried and “researched” up to now in the case was done in native Calc (stored to .ods when stored at all) from the beginning and exemplified for myself with a XY-chart containig two Y-series.

The com::sun::star::chart::ChartDataCaption::CUSTOM element was introduced in the fix to that bug.
I don’t know anything else about the question (and I didn’t know that much, before checking git history), thus I didn’t add anything substantial.

For me this is surrounded by some additional problems (and little projects) where there is no progress.