Man pages matching name qwtplottradingcurve in section 3:

QwtPlotTradingCurve.3.en	debian 10 / libqwt-doc
QwtPlotTradingCurve.3.en	debian 11 / libqwt-doc
QwtPlotTradingCurve.3.en	debian 12 / libqwt-doc