Fade length in percent?

WaveLab
1

Just bought wavelab pro 12.
I found no way to set the fade length in percent, what is really bad especially for batch processing?
Is this true?

Thank you..

2

Percent of what?

3

Fade length in percent regarding to the sample length. Fade out length of 50% would be 500ms of a file with a length of 1000ms.

4

This is the first time I hear such a request.
I don’t see the audio interest. Especially for batch processing.
What is your use case?