Given any position p, p.h is the headline text of p.v, and p.b is the body text of p.v.
p.h and p.b are Python properties, which means you can set the headline and body text by assigning to them:
p.h = p.h + ' more'
In order to see the result of changing a headline, Leo scripts must redraw the outline pane, like this:
c.redraw()