Split fittype command onto multiple lines

I have a fit that I'm conducting that is on a very complex equation. It would really simplify any modifications if the line of code that is over 4,500 characters long could be split into multiple lines. I have attempted to use the continuation (...) without success. I have tested it on simple commands: (A=5*...[new line](2+6)) for example and it works just fine. Anyone have any idea how I could split my fittype expression onto multiple lines? Thanks in advance for any help.