Summary Generation Commands

Y g: Regenerate the current summary buffer (gnus-summary-prepare).
Y c: Pull all cached articles (for the current group) into the summary buffer (gnus-summary-insert-cached-articles).
Y d: Pull all dormant articles (for the current group) into the summary buffer (gnus-summary-insert-dormant-articles).
Y t: Pull all ticked articles (for the current group) into the summary buffer (gnus-summary-insert-ticked-articles).