Man pages matching name qwtplotdict in section 3:

QwtPlotDict.3.en	debian 10 / libqwt-doc
QwtPlotDict.3.en	debian 10 / libqwt5-doc
QwtPlotDict.3.en	debian 11 / libqwt-doc
QwtPlotDict.3.en	debian 12 / libqwt-doc