Dummy Playback Playing Technique?

When creating Playing Techniques for missing symbols, is there a “None” Playing Technique? Because if I’ creating musica ficta or bracketed fermata, I don’t want to change any techniques that are currently in operation.

Or do I have to create one?

No, there’s no dummy playing technique, but you could certainly create one. Provided it doesn’t map onto anything in your expression map it won’t do anything anyway.