Yes, design extender will be compatible with DW CS6.
you will need to edit the database conenctions file, in the Connections folder.
the last line will look similar to this:
$wadb = mysql_pconnect($hostname_wadb, $username_wadb, $password_wadb) or trigger_error(mysql_error(),E_USER_ERROR);
where wadb is the name of the connection.
$wadb = mysql_pconnect(
and remove the p:
$wadb = mysql_connect(