I’m not sure I understand the question.
You know how to:
Edit the L/R balance of a track in the timeline using the mixer or keyframes
I assume you want to:
Change the balance of a single clip so it is always applied like that as you add it more places in the timeline, or other timelines in the same project.
If that is the case, then the answer is not really. There is very little L/R control when it comes to interpreting footage (right click your clip in the bin, go to Modify > Interpret Audio). In multichannel audio you can move what channel goes to what speaker (with no percentage mixing), and mono tracks can either come in as stereo hard panned to one speaker or the other, or as cloned stereo which feeds both speakers with the same track.