I just had the same issue and I was able to make the calculations option appear.
In the case of some of my courses the Show calculations options was off but in the case of others it was on and the edit calculation option was still not available.
If the first case applies to you, turn it on and save the changes. If the second case applies to you, turn it off, save the changes, then turn it back on and save again.
To find this option, follow the steps in the attached image.