Make sure the marker is selected, then go up to the upper right and Name it.

BTW - if you have the marker in the wrong place, you can move it after the fact - I was wrong, you don't have to have it EXACTLY in place when you first place it, but you get the idea - it'll place the maker exactly where the play-line is sitting.

I hope the helps, and you have fun making DVDs and BluRay discs-

-Lew