The Geometry menu

Geometry toolbar
display the geometry toolbar as secondary toolbar
Orient
orient the selection in a set of preset directions
Flip
flip the selection.
Flip drawing
flip the current drawing.
Center drawing
move the current drawing to the center of the page.
Straighten base
Make the selected single strand, or the single strands at the base of the selected helix straight.
Straighten top
Make the selected single strand, or the single strands at the top of the selected helix straight.
Arch
curve single stranded areas
Redraw helices
Redraw all selected helices.