I think you can set the default time for a transition. Go to Edit/Preferences/General.
But whether or not your transition will center at the cut depends on the characteristics of your clips.
As I explain in my book, transitions need to borrow about half a second of material from beyond the out point of one clip and the in point of the other to create the transitional segment. If one clip has that extra footage and the other does not, the transition will favor the clip with the transitional material unless you force it otherwise.
And, during slideshows, transitions will often rest off-center by default.