This is in version 13.2, 64-bit.
If I do "edit table_a" I can edit the data in the grid and the "green light" is lit, as in my old version of Toad.
If I do "edit table_b" the grid is read-only and the editable-icon is red.
The only difference I have found between the two tables is that table_b is index-organized. Would this affect the ability to edit it's data?