The contextgarden tells me under Command/placefootnotes
Place unplaced footnotes. Has no visible effect if location=page, but can be used to place footnotes (or endnotes) made when location=text was in effect.
However nothing happens for an \endnote, but it works for a \footnote. See minimal example.
Minimal example:
\setupfootnotes[location=text]
\starttext
abc\endnote{an endnote}
\placefootnotes
\stoptext
ConTeXt ver: 2013.03.20 10:34 MKIV fmt: 2013.3.20 int: english/english