underliner
/ˈʌndəˌlaɪnər/Definitions
1. noun
A person whose job is to underline or highlight text, especially in books or manuscripts.
“The underliner carefully went through the manuscript, adding emphasis to key points.”
2. noun
A tool or device used to underline or highlight text, especially in writing or art.
“She used a fine-tip underliner to create intricate designs on her sketchpad.”