On Windows with WaveLab 11, even if the option : “Locking Fade Times When Adjusting Clip Edges” is checked, this option is not working on my setup. That was so useful on my old WL6 
AFAIR, there is no lost feature. To achieve what you like, maybe you should need this:
Still not working. I tried again many menu/option combinaisons… It should do it for fade-in and fade-out… Are you on a Mac ? Could that be a bug on the PC version ?
Regarding this feature, what exact procedure you could you do in WaveLab 6 and that you can’t do with WaveLab 11 ?
Here is a short video with 2 actions (that doesn’t work in my WL11) :
1st : “Locking Fade Times When Adjusting Clip Edges” with this option you make your clip smaller, unclick, click again and the point become locked and you can do your fade-in/out lenght with moving theclip side.
2nd : In the inverse way, if I want to make my fader longer or smaller, point can’t be locked (always following the clip side and keep the same lenght. (whatever the option i clicked or unclicked)
Thanks for your help !
Well, point #1 is not there anymore, I think because this is a strange way to make a fade (from where I stand, this even looks like a WaveLab 6 bug (?))
Point #2 is still possible:
Well, so bad for point#1 : It was definitely not a strange way to make a fade ; that was a really fast way to build an audio montage clip trim. That was a “tip and trick” from a few major mastering engineer…
So, there is a lost feature 
Thanks for point#2 answer.