Non-Pitched, Rhythmic Notation for Voice

Maybe using slash notation?

I would personally use rhythmic slash notation - see the Handbook under "Tools". You can also simply enter the notes at whatever pitch you like and then apply a custom notehead from the palette, maybe also use the Inspector to turn off the "Play" property. Up to you how you want it to look. Feel free to attach a sample of what you'd like to achieve if you have something specific you are trying to duplicate.