What computer operating system is your Premiere Elements 12 running on? Have you updated 12 to 12.1 using an opened project's Help Menu/Update? If not, please do so.
Now to the matter at hand....
What specific video transition do you want to reverse?
Generalizing for now....
Apply your video transition between your two clips
When the Transition Adjustments Pop Up pops up, click on the More button
If that particular video transition offers a Reverse option, "Reverse" will be at the bottom left when you
are in the More section. Place a check mark next to "Reverse". Example - See Page Peel/Center Peel.
I did update to 12.1 and I'm using Windows 7 operating system. I am trying to reverse the Center Shape Transition. I do not see a more section nor do I see a Page Peel/Center Peel Transition to view an example of how it works. Is there some other software that I need to install??
Thanks for your help
For the bottom line, please read the end of this post first.
We seem to be out of sync on both sides. You see no Page Peel/Center Peel Transition, and I am not seeing any "Center Shape Transition".
If you have Premiere Elements `12/12.1 on Windows 7 (presumed 64 bit), you should see the following categories under the Transitions Tab (Expert
Please note the Page Peel category in the line up. If you click on Page Peel, you will bring up its choices
When you apply the Center Peel transition between your two Timeline clips, the Transition Adjustments pop up More should reveal a Reverse option
for this particular transition. Not all video transitions have a Reverse option.
Click on More and scroll down to the bottom of that section to see
After all of the above, I just figured this out. You are not in Premiere Elements 12/12.1 Editor. You are in Elements Organizer 12 Slideshow Editor. I do see one of the transitions there named "Center Shape". That looks like your "Center Shape". I am not seeing any way to reverse the video transition in the Elements Organizer 12 Slideshow Editor.
Photoshop Elements 12 and Premiere Elements 12 are standalone programs, each coming with an Elements Organizer 12. When both are on the same computer, they share the same Elements Organizer 12. If you want to get into reversing transitions, then I suggest that you create your slideshow in the Premiere Elements 12 Editor after you confirm that the transition there does offer a reverse option.
Please review and consider.