I'm not entirely sure what it is you want to accomplis, but this:
man 5 exports | col -b | grep '^ [ ]*/'
greps the example lines from the exports manpage. Placing >> /etc/exports will append the output to the /etc/exports file.
But these lines from man exports are examples and need to be changed for your particular setup.
BTW: It would be easier to have 2 terminals open, one for editing the /etc/exports file and one with the man page. You can copy/paste the parts you need.
Hope this helps.