Hello.
I would like to have that in the crossfade menu
(Sorry for german speech)
you can choose from the different crossfades/transitions that are in the pack.
.prfpset files are already supported by Shotcut.
Now it"s time that we can choose from these transitions AND
also can choose the speed of the standard crossfades that are already in shotcut, please.
These crossfades are too slow, i want to speed them a little bit!
Hope you understand what i mean! 
This is already possible changing the duration of the transition. This is the only way you will ever be able to change the speed. It does not make sense for the transition to run faster and then remain suspended until the duration of the transition. Likewise, it does not make sense for the transition to run slowly and then abruptly stop before it completes. You change the duration of a transition by dragging the green edge on its left or the right edge on its right.