Each of these start-commands has a corresponding stop-command which should be used at the end of the section. For example:
<context mode=mkiv source=yestext=produces>
% mode=mkiv
\setuppapersize[A5]
It is also possible to set per-section variables, and retrieve them with the {{cmd|structureuservariable}} command:
<context mode=mkiv source=yestext=produces>
% mode=mkiv
\setuppapersize[A5]