What computer operating system is involved with your Premiere Elements 13? Have you updated 13 to 13.1 yet using an opened project's Help Menu/Updates?
To your immediate question.
I have not looked into the miniature effect for video before, so I took a quick look at what information was available online.
The effect looks like a selective blur effect. Is that what you seek? If so, look into Clip Menu/Effects Mask where a blur effect is applied to the mask.
I will do some more searching to see if there is more to that effect than just selective blur.
Please give details.