By default the hash navigation has already a smooth scroll effect. If you are expecting for another behavior then that will require some customization. Regretfully, customization is outside the scope of our theme support. You may seek 3rd party developers to help you with your problems or you can avail One where we can answer questions outside of the features of our theme.
I’m fully aware that the effect already exists. What I’m wanting is to modify that behaviour to take into account the height of any fixed/sticky headers.
If there’s no solution already I’ll code it myself and post it here for the community to find. Just thought others in the community may have already requested this.