How to add "two" transitions between clips in Premiere?
I am unclear on what you are asking. So you have 2 clips on your timeline and you want to have clip 1 dissolve but only halfway? That's your opacity. So just click on your clip in the timeline (next to the clip name I believe there's a twirly) and you should be able to select motion, or opacity. Click opacity. Then adjust it with keyframes.

Then go to your second clip and start your first keyframe at 50% and then further along the timeline take it back to 100% with another keyframe?

I hope that helps.