Using FP5 on a PC: To copy a field I seem to have to first switch to a layout that displays the field not just be in a file that has that field.

Is that right?

Yes, that's right ... Use Set Field () instead, that's not layout-dependent

I'm not sure that will work. I am generating a canned email which I believe that I need to paste the text manually.

It must work using the Set field () step, the only thing you'll lose is text formatting ... if you're copying text into the clipboard to be used outside FileMaker that's a different matter

If you're sending email, if you use Send Mail script step, you can use text from fields to fill out the email message, including To, CC, BCC, message body (up to 256 characters) and file attachment. Then you won't have to use copy & Paste or Set Field.