Marking layout lines with a pencil always leads to "Do I split the line or save the line?" Here's a way to narrow the line, but still be able to see it, and resolve the issue.
Use a piece of sandpaper to create a flat side on your sharpened pencil then ride the flat edge along your straightedge. The line you create will be the exact the location of your cut. I mark dovetails this way and transfer lines from pins to tails. It is surprisingly precise. It does not, however, allow you mark lines in tight quarters, as in transferring marks from tails to ultra-thin dovetails. For that, you need a thin-bladed marking knife. (Or, cut your pins first...but that's another post.)
Using a pencil with a bevel edge leaves a mark that is easier to see than a knife mark. Sometimes you need that, especially if you've reached that 40+ year old bifocal age (raising hand).