Problems with data labels in charts

Hi all,

as far as I understand, we have currently this situation:

Graphic properties
----------------------
A data label is created as css.drawing.TextShape and as such it can have 
FillProperties, LineProperties and ShadowProperties.
In ODF, a data label is a <chart:data-label> element and its style can 
have graphic properties.
The data labels in MS Office have graphic properties too.

Our model has no explicit data labels, but all about data labels is 
contained as properties in a data point or as default in a data series. 
But data points and series have graphical properties themselves. So when 
graphic properties for data labels were introduced (such doesn't exist 
in OOo), new properties of kind "LabelFillColor" were created, see 
https://opengrok.libreoffice.org/xref/core/chart2/inc/unonames.hxx

This graphic properties are written to ODF in loext namespace into the 
style of the data point or series instead of writing into the style of 
the <chart:data-label> element. That is wrong.
If a data label gets graphic properties in MS Office and the file is 
written to ODF by MS Office, then the properties are correctly in the 
style of the <chart:data-label> element. But LibreOffice cannot 
interpret it.

Position
----------
The user can drag a data label to a different position. This corresponds 
to "CustomLabelPosition". Latter is relative to the position calculated 
from the "LabelPlacement". (Do I understand this correctly?)
ODF has for a user defined position the attributes svg:x and svg:y of 
the <chart:data-label> element. These describe the position relative to 
top/left of the entire chart.
MS Office uses these attributes in its export to ODF.
(OOXML has the element manualLayout, but I do not understand its unit.)
LibreOffice allows the user to drag the data label, but does not write 
the new position into the ODF-file at all and therefore has it lost on 
reopening.


So there are discrepancies between what LibreOffice writes and reads and 
what exists in ODF. What to do?

Kind regards
Regina