Maybe through scripting?
(IN JMP 12 at least) 'Explore Outliers' is not a real platform, so the ways in which it can be manipulated via JSL are a little limited.
Stating the obvious perhaps, but 'Explore' connotes an interactive usage pattern. So you might be able to get close by assigning the 'By' variable to 'Rows > Data Filter' with 'Show' and 'Include'. Note, however, you need to press the 'Rescan' button in 'Explore Outliers' whenever you change the level of the 'By' variable.
That sounds very doable. I fact, the results might be easier to work with
than by-groups would be. Thank you.