Just tried out the app and it seems very useful! (although he GUI is a cluttered, confusing mess, LOL).

I was thinking, it would be super helpful if the line reader had a 'snap' feature, where for example, if I have just the line feature active, and I move the cursor over a line of text, it would automatically snap the line below that line of text for me for an actual underscore effect. It would help reading immensely because it would snap line by line as I read rather than just sort of floating wherever I move the cursor, often covering the actual line.

I'm not a programmer so I don't know the logic behind the code, but I know for at least web pages that use CSS, there is often a line-height directive that could maybe be read by your program to know the exact height of each line to aid in knowing how to snap below the line?