Materialized View Query is editable in SB RHS for SB|Mat. Views. This is also a bug in 12.8 GA version.
Some MVs can be updated. This, for example:
CREATE TABLE TABLES AS SELECT * FROM DBA_TABLES;
ALTER TABLE TABLES ADD (
CONSTRAINT TABLES_PK
PRIMARY KEY
(OWNER, TABLE_NAME);
CREATE MATERIALIZED VIEW LOG ON TABLES
WITH PRIMARY KEY;
CREATE MATERIALIZED VIEW TABLES_MV
REFRESH COMPLETE ON DEMAND
WITH PRIMARY KEY
FOR UPDATE
AS SELECT * FROM TABLES;
Oops! You mean the query tab! Got it. Thanks.