Higgs Boson wrote:

I am looking for ways to "soften" in order to be able to manipulate the
stiff and "recalcitrant" edging to make it conform to the small
rectangular bed to be edged.

For a *rectangular* bed why are you bothering with "free-form" type
edging? Seems to me a trip to the lumber yard for some landscpape
ties is in order. Instead of an image of that fercocktah product post
a picture of the bed you want edged. In my experience free-form type
edging doesn't work for straight lines, no matter how many pegs are
used it always ends up crooked. And if you live where the ground
freezes no flexible edging works.