Your best options are to write a visual .Net control (MS Charts) and wrap it as an ActiveX or use a third party solution like for example FusionCharts. Here's a post (from 2008!), where someone already found them outdated:
https://sites.google.com/site/lovepb/pbwithfusioncharts
Appeon promised us to improve and modernize the current charts, but "all they did" was to allow customised softer colours, which was already possible to do by code anyway. So quite a bummer on that one.
I've used FusionCharts in the past and you'd need the MS browser control or the new control based upon the Chrome engine (pb 2019 R2) to be able to show them. If you want drill-down functionality, it's possible: you just generate the html/xml on code. A lot of work, but perfectly doable.
Others have implemented Google Charts: https://community.appeon.com/index.php/qna/q-a/use-of-google-charts-in-power-buldier (this is mobile only example, but I'm sure you could get it working on Classic PB).
Some people use the charts which come with Excel but then you need to have office and I found that the ActiveX which comes with powerbuilder and allows to use Office visual controls, are no longer functional with current office versions.
Not sure if Telerik or Syncfusion might have easy to implement charts (not cheap probably, but maybe you already have a licence).
thanks for this suggestion, I will try this out, but would be great if nice graphs are part of PB!