How do I add elements to a node view? In Drupal 8 routes like entity.node.webform.user.submissions (path such as /node/2/submissions), entity.node.webform_submission.canonical (path such as /node/2/submission/118) etc etc display entity view in the main content block. My question how would I append/pre-append/insert html elements (such as link tag,submit button, textfield etc etc) in the entity view.For example if the view shows a table listing submissions how to pre-append a link button at the top right corner of the table.
I have tried:

function my_module_entity_view_alter(array &amp;$build, EntityInterface $entity, EntityViewDisplayInterface $display){
    kint($build);
    kint($entity);
    }


In kint($build) and kint($entity) I can't see any part where to add HTML markup. How and where should I add it?
The Webform module for Drupal 8 does not fully support display modes.  To alter a submission's HTML or text you will need to use hook_preprocess_webform_submission_html() and hook_preprocess_webform_submission_text().

I created a ticket on D.O. to look into this issue.