https://forums.oracle.com/forums/thread.jspa?threadID=447344
The pertinent section reads:
There’s no setting to fetch all records. You wouldn’t like SQL
Developer to fetch for minutes on big tables anyway. If, for 1
specific table, you want to fetch all records, you can do Control-End
in the results pane to go to the last record. You could time the
fetching time yourself, but that will vary on the network speed and
congestion, the program (SQL*Plus will be quicker than SQL Dev because
it’s more simple), etc.
There is also a button on the toolbar which is a “Fetch All” button.
FWIW Be careful retrieving all records, for a very large recordset it could cause you to have all sorts of memory issues etc.
As far as I know, SQL Developer uses JDBC behind the scenes to fetch the records and the limit is set by the JDBC setMaxRows() procedure, if you could alter this (it would prob be unsupported) then you might be able to change the SQL Developer behaviour.