Add underline style setting to Factbook visual filter

Can we make it user customisable?

Being able to change that would be a great help, have a hard time seeing it on my laptop and nearly impossible in dark mode.

This is extremely faint in dark mode. Initially, I thought the feature was missing from my download. I had to switch from dark mode to see the factbook markings. A bright color would be much better or make it customizable.

I agree with all the comments.  we need a customizable underline.  even if it is just to increase either intensity or thickness of the underlining.