If the “Some Notes Do Not Belong To Voices…” dialog appears

When you click Apply, a warning may appear saying “Some notes do not belong to any voice and may be hidden. Correct these notes?”.

This warning appears when the staff contains notes with MIDI channel settings which do not match any of the active voices.

If you click the “Correct” button, these notes are moved to active voices. If you click “Ignore”, nothing is changed, and some notes are hidden. However, they are not lost, they appear in all other editors and can be made to appear again in the Score Editor if you change the channel settings for the notes or voices, activate more voices, etc.