theres a button in 'items' => 'town run' => 'always stash ancients' (in the current public beta version, at least)
or to only keep specific ancient items, use the 'items' => 'item list' => (item) => 'must have properties' => (check) 'Ancient' *and* 'items' => 'itemrules' => 'use rule set' => 'custom* rtfm!'