One very nice DadaMail feature is the ability to change your email
address in all subscriptions at once using the /dada/extensions/ update_subscription cgi However when you do, all the other added
subscription fields are blanked out I don't recall if it was doing
that before this latest update

It was:

http://dadamailproject com/support/documentation-dada-3_0_0/dada2_to_dada3 pod html#extension__update_subscription_cgi

I don't really like this extension, since there's no check that the
person doing the update is the actual person who owns the email
address A better thing would be, instead of updating this extension,
is just to go forward all away with the, "Allow list subscribers to
update their own information", feature in Dada Mail, which would
include email subscriptions It doesn't even need all the session
management I write about in that feature, just another confirmation
process, almost exactly like the subscription confirmation, exactly
it'll update the subscription

If you do want to fix this bug and are comfortable with the idea that
there isn't any, "Are you really the subscriber?" check, find these
two lines in the, update_subscription cgi extension:

$lh->remove_from_list(-List => $_,  -Email_List => [$old_email]);
$lh->add_to_email_list(-List => $_, -Email_Ref => [$new_email]);

And replace them with:

my $sub_info = $lh->get_subscriber(
    {
        -email => $old_email,
        -type  => 'list',
    }
);  
$lh->remove_subscriber(
        {
                -email =>  $old_email,
                    -type  => 'list',
        }
);
$lh->add_subscriber(
        {
                -email  => $new_email,
                -type   => 'list',
                -fields => $sub_info,
        }
);

and the subscriber fields information will be retained