I have my script output set to have certain key words lower case in any editor also in script (F4 describe & script tab). i can copy and my script from the Editor window and the lowercase is carry over to my paste output (notepad). When I copy script from Describe window into notepad everything is back to "uppercase".
Copy and paste the script by right click a table from the schema browser | select Create script | select option for output "Editor as Script".
This will load the script into the Editor window, here you can copy and paste it with the lowercase carry over to the notepad.
Waiting for fix in future release of Toad for Oracle.