When to use Compare Settings
Use the Compare Settings tool whenever you are unsure of what settings will give you the best results. For example, you might want to see how effective different Sensitivity settings of the Declicker module are at cleaning up a file. Or maybe you want to hear if Denoiser's highest quality (C) algorithm gives you noticeably better results than its faster modes.
Sending settings to the Compare Settings Window
Set controls in the module you are using then hit the Compare button. RX will open the Compare Settings window, and will begin processing the result of those settings in the background. Repeat this step with other control settings or processing modes in the module, and RX will add a new item to the list each time you hit Compare. These will be given default names, but you can use the Rename button to choose friendly names for the items in your Compare list.
Previewing settings side by side
Once you've populated your Compare Settings list, clicking Preview in this window will play the selected settings. In addition, you will be able to see the result in the waveform and Spectrogram Display, allowing you to see at a glance how these settings affect your audio.
Once you've compared the items in the list, you can select the best result and then hit Apply to commit those settings to your file.