I’m sure @DaveR will chime in soon with a more detailed explanation of why there is almost never a reason to change the active tag/layer and to do so is to invite disaster. I’ll give you the quick basic version.
Tags (used to be Layers) only control visibility, they do nothing to physically separate geometry within SketchUp. That job is accomplished using groups and components It is a basic concept of Sketchup that all raw geometry is “sticky” and can interact with all other geometry. So, if you make a line of raw geometry and put it on some tag, even if you turn that Tag off it can still interact with, distort, cut, destroy other geometry that occupies the same space, even while invisible. People often get distorted confusing models that are falling apart because invisible geometry is merging and distorting geometry that they can see. So it is best practice to only place already “sealed” containers of groups and components on separate tags, and to leave all raw geometry untagged where it’s relationship can be seen and carefully managed.
You can make a group of your tracing lines and give that a separate tag, then open the group to trace more or edit, no prob.