Octave (Ottava) lines are used to indicate that a section of music is to be played one or more octaves above or below written pitch: The line may be dotted or solid. Ottavas are available in the Lines palette of the Basic and Advanced workspaces.
8─────┐or 8va─────┐: Play one octave above written pitch
8─────┘or 8va─────┘: Play one octave below written pitch
8va alta/bassa lines are particularly common in piano scores, though they are sometimes used in other instrumental music.1 15ma alta (2 octaves above) and 15ma bassa (2 octaves below) are also occasionally used.
MuseScore automatically adjusts playback of the score under the ottava to the correct pitch.
And to adjust the vertical position, see Lines: Adjust vertical position.
See Lines: Change length.
Ottavas can be customized just like any other line. See Custom lines and line properties.
Properties unique to Octave lines can be adjusted in the Ottava section of the Inspector: