Hello,
Can you please provide a short code example? I tried the THEN with a PL/SQL IF statement and it should work well. Did you mean that the "Position THEN on the same line" in the Newlines tab (in the formatter option menu) is not working?
About string concatenations: in the option menu you'll find a tab String Concatenation (in the Operators & Punctuations menu) which should provide the options you want.
Hope this helps,
Andre