When you are working on an audio file or clip in WaveLab Elements, you can open the project of the audio file in Cubase/Nuendo. This allows you to correct issues that you have identified during mixing and correct these issues in the audio file in Cubase/Nuendo.
When you then export the audio file in Cubase/Nuendo, and you use the same file name, the audio file or clip is automatically updated in WaveLab Elements.