<I don't know if this will solve it...>
1,Create two patterns of bolt sets. (With and without washers)
2,Create an END CODE specifically for carbon flanges.
3,Assign the above END CODE to the flange or valve to which you want to attach the washer.
Then, try applying the video below.
https://www.youtube.com/watch?v=ofRqD3eidvA
It's in Japanese so please watch with English subtitles.
Regards,
Shuji Sakuma From Japan