This works for me. Can you provide a use-case example?
open a sql work sheet logged in as the owner of the table in your query.
select * from my_table;
right click anywhere in the my_table identifier and select open declaration.
sql developer does nothing.
I see this not working in EA - 'Only 2 records will be displayed...' error message, but I do see it working in what will be EA3. So it appears to be fixed for the next release.