(They display nowhere, have no effect - and new ones, though effective for the session, cannot be permanently saved.)
The "Exceptions" window (in custom settings for history) is empty.
They're gone from the "Permissions" pane of "Page Info".
New cookie permissions could be created for the current session, but are gone after a restart.
After rolling back to Basilisk-20180321, the cookie exceptions came back like normal.
(For clarity, brand new exceptions created in v20180424 did not come back, but all earlier ones did.)
Tried a new profile: same result.