Why can't NWC change differing note durations in a selection? If NWC supported it, correcting tuplets would be much easier.
Probably because you're dealing with version 1. You can do this in version 2.
Perhaps user111 was referring to a feature by which the "as played by MIDI" note duration may be different than the nominal (sheet music) note duration? Or, was it the ability to change visible note durations with a more flexible variety of user tools (NWC2)?