Increase span length by number of beats.
Number of beats.
Create an invisible extension.
Create as long extension line as possible.
Increase length of extension length by given number of measures.
Number of measures.
Increase extension length by note length multiplied by number of notes.
Length of note (e.g. "2n").
OptionalnoteCount: number
Number of note lengths (default = 1).
Etension builder type.