The “highlighter pen” doesn’t really highlight. It still screens out the base image. What the highlighter function needs to do is have more of a “multiply” effect on the image behind (see Adobe software, photoshop, AI, INDD).
Also, the pen is good, but often I need to highlight in a straight line, or simply draw a region. If the region function has a “highlight” button on the opacity that clicks it into a multiply mode, that would do it.
