Man pages matching name qwtplotpicker in section 3:

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