Write three lines in a SQLWorksheet
test test2 test3
Now Edit -> Replace search for \n , replace with nothing and make sure Wrap Around, Regular Expression and Scope All are checked and click OK.
Result: The search text "\n" was not found and my lines are left untouched.
Now select all the three lines, repeat the same replace (Selected Text Only is automatically checked, which is an improvement over older versions) and click OK.
Result: The search text "\n" was not found but my lines are correctly replaced:
The same problem applies when editing packages.
SQLDev 18.104.22.168.27, Java 1.7.0_21, Mac OS X 10.8.4.