Right now, one can set Flex/Exact searches on a tab by tab basis in "single text" searchtabs, but not in Search All Tabs. Search All tabs use the "Search Tabs" Preferences settings to determine if a Flex or Exact search is done. The only way to change it is to change the Preferences setting. This is cumbersome and counter-intuitive.
I prefer to use Exact searches in "single text" search tabs, but Flex search in Search All tabs. doing so means resetting the preferences whenever I use a Search All tab.