is it possible to write a custom string instead of the x and y position over a ScatterPoint? I searched in the documentation and Google but sadly didn't find anything. :/
Yes it is my friend!
If you want the custom string to be the same for all points in the series, simply edit the TrackerFormatString. The TrackerFormatString is in the series object.
If you want each point to have a separate string, add the tag to the custom string like so:
seriesToAdd.TrackerFormatString = seriesToAdd.TrackerFormatString + "{Tag}";
You can then edit the tag for each point in the series.
Hope this helps!