#24801 needs to be fixed so we can depend on right clicking. I think SET and CLEAR should be replace by TOGGLE (#22083). The patch for #17535 already includes marking breakpoints in the margin.  I am opposed to a putting a symbol on every line.  Too noisy and too confusing to beginners for an advanced feature.  There are other things that could be added to a line-number context menu, such as cutting or copying a line without having to drag select it (which is too easy to mess up).