Sometimes when I am working with alias of a public synonym, the dot lookup doesnt work.
SELECT * FROM emp e where e.
Given, that emp is a public synonym, when I type e. no column shows up after the period.
The issue with the dot-look up has to do with not only using a synonym with the same name as a table but also not ending queries with a semi-colon.
Make sure you end all queries with a semi-colon.
Waiting for fix in a future release of SQL Navigator.