Answer by Fareed A.S.:
At least until Primavera P6 Professional 8.4 it was not possible, and I am quite sure it won’t be in the latest P15 version. The reason is that the application is not monitoring the calculation/completion of any activity by itself. The user has to specify all those things, including specifying when any activity is supposed to start. You may have a plan to start Activity-2 after Activity-1 is 50% completed. Let’s assume it is even programmable in some software application. But how will the application know that Activity-2 did indeed start when Act-1 reached 50%? This was with regards to progress. In terms of only the plan, doing this would need some kind of programming at the back end which would involve an If-Then-Else-ElseIf kind of selection criteria or something even more complicated. What we have noticed over a considerable period of time, software applications tend to make things easier in every successive update, not the other way round…. but that’s not to say that it can’t ever be done. Just for the sake of doing it? Yes, it can be done. But that feature is yet to be added.
To answer it plainly, you cannot do it in terms of predecessor percentage, at least not at present. The only way is to do the link manually, at least for now.