You can input octave lines using the Clefs panel, both during note input and by adding them to existing music. You can also input octave lines only into specific voices in multiple-voice contexts.
These steps describe inputting with the default mouse input preference Create item at selection.
Procedure
Result
During note input, octave lines are input at the caret position. They are input with a default duration of a quarter note.
When adding octave lines to existing music, they are input either above or below your selection, depending on whether the octave line indicates that notes are played higher or lower than notated.
The pitches of notes within octave lines are adjusted automatically. For example, notes within octave above lines appear an octave lower than they do without the octave above line.
You can also lengthen/shorten octave lines after they have been input.