[Radiant] Adding "extended" content to existing page?

[Brian Capouch]

Newb here.  Doing my best.  I've spent many hours trying to figure this 
one out, so far w/o success.

Is there any way to "extend" an article once it's written.

By that, I mean to show only the first part of it and let the "Archive" 
parent page print that part and then provide a "Read more" link.

I used the default site provided with the gem install, and then edited 
the resulting pages.

I didn't notice until afterwards that while *new* child pages I create 
under the main Articles page have both "Body" and "Extended" parts, the 
existing pages (which I edited) did not.

I'm confused as to who decides that gets put there, and how, and whether 
it is changeable after the fact.

Thanks for any pointers I might elicit.

B.

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