I suggest that OpenMPT could have a "multichannel cursor" feature.

A multichannel cursor means that an edit cursor (in the pattern edit view) is displayed and inputs data onto various channels at the same time.

This makes editing more handy especially when working with multichannel chords or unisono patterns. For example, if volume or vibrato commands & values are supposed to be the same for every channel on which a chord is spread, a user can just type data once and it will appear on every channel on which cursor is shown.

By pressing a hotkey which activates multichannel cursor, user could switch between 1-4 channel modes for the input cursor (1 channel mode is the normal).

Of course a user can do the same by using copy & paste but I'm pretty certain it involves many more key presses in some cases. This feature is not by any means obligatory but I think it would a nice addition and probably significant share of users would utilize it.