Short version is that you have two options:
- What @bachstudies mentioned, inserting visualizers to see the effect in realtime (Spectral or otherwise depending on what you want)
- Develop a visualizer in Noise Repellant to see it in realtime (This is the option used by most commercial plugins) (EDIT: To be clear, this means programming and submitting the code to Noise Repellant, I don’t believe this functionality exists right now)
By intention you won’t ever see the waveform change in Ardour as Ardour does not destructively change the audio. There is no way to do it via plugin or otherwise right now and it is likely this won’t change in the near future as it would indicate destructive changes on disk and would require a rerender every time any little aspect of the plugin is modified as Ardour can’t know what would need it or not. This is antithetical to Ardour’s design.