Cadenzas: How do you make one?

Music theory has brought about many challenges for an app to solve, and Noteflight solved every one of them.
However, one thing has stumped me. How do you create a measure-bar-less cadenza? Invisible measures still requires the cadenza to end an exact amount of beats, and that seems restrictive.

I think if cadenzas cannot be created, there should be a new option or add-on to the time signature option to make a cadenza, where there could be an unlimited amount of beats in a measure.