Have you asked this question here before?
On what computer operating system is your Premiere Elements 12 running on? Have you updated from 12 to 12.1 yet using an opened project's Help Menu/Update? If not, please do so.
But, as to your immediate problem and assuming that you are using Windows 7, 8, or 8.1 64 bit computer....
As you hold down the Alt key of the computer main keyboard, make your additions carefully to the existing Timeline content. Premiere Elements does not have any locked track feature. In some instanced, you may want to select (all at one time) a group of clips to move them as a group. Or, you could select (all at one time) a group and apply the Clip Menu/Group command for a permanent grouping of that particular group of clips.
You can select clips (all at one time)...
a. Hold down the Shift key and click on all the clips you want selected all at one time
b. Using the mouse cursor, draw a rectangle around the clips to be selected in order to select them all at one time.
Any questions or need clarification, please do not hesitate to ask.
Thanks! The Alt key did the trick! I've divided up my song in the soundtrack so many times and wasted so much time putting it back together or reinserting it. I really appreciate your help and how quickly you responded.
Is there a way that I can set it as the default so that I don't have to push alt every time I move a video?