Use case:

When user is editing a long note and want to add a line in the middle.

Currently I believe users would have to select everything below that line and move them downwards, which would involve zooming out, selecting, moving and zooming in. A bit troublesome.

Hope to add a spacer tool, when activated, users can click on a spot and a horizontal line would appear. When dragging the horizontal line, all the content would move with the line. This would provide users a much easier way to insert a line of note.