The most intuitive approach is to draw a line shape.
But that would have a problem , When you add some content before the line shape , the line shape does not move relative to the content.
So we finally used “_________________” instead horizontal line.
OneNote Gem provides this function.
1. Horizontal Line
This feature will insert a horizontal line.
This horizontal line large then portrait, and less than landscape.
It can shorten or stretch by drag outline.
2. Adjust to Landscape Horizontal Line
Justified the Horizontal Line to fit for size of landscape page (A4) to print.
3. Adjust to Portrait Horizontal Line
Justified the Horizontal Line to fit for size of Portrait page (A4) to print.
Warning: After adjust to Landscape or Portrait, the Horizontal Line can't resize by drag outline until you restart OneNote.