The alt-shift-x command toggles highlighting of cautionary accidentals.

By pressing alt-shift-x, you can toggle the display of cautionary/courtesy accidentals. Cautionary accidentals are those not strictly necessary, except in performance editions where performers are reminded of changes in accidentals from previous states.

Here’s an example of cautionary accidental highlighting after using the alt-shift-x key combination:

displaying cautionary accidentals.
Highlighting cautionary accidentals after pressing alt-shift-x.

View example score in VHV: Vivaldi, op. 1, no. 1, mvt. 5

Pink accidentals represent cautionary ones. In measures 2 and 3, accidentals aren’t really necessary since the same pitch has already been altered previously in the measure. However, repeating the accidental can help prevent performers from playing the note with the wrong accidental. The E-natural in the sixth measure is typically required in modern editing standards due to the E-flat in the previous measures. In modern accidental interpretations, the accidental for the first note in this measure for the Violin part is automatically E-natural. However, the previous E-flat may cause the performer to play an E-natural, or they may wonder if the flat was ommitted accidentally.

This feature is also useful for editing scores to decide if cautionary accidentals are necessary, and the highlighting allows quick identification of existing cautionary accidentals to focus on.