I want to add a custom tab after "Edit" but can't figure out how to do so. I added a mymodule.links.task.yml file
entity.node.import_form:
route_name: entity.node.import_form
base_route: entity.node.canonical
title: Import JSON from file
But I don't understand what to do next. The node form just errors out with:
Symfony\Component\Routing\Exception\RouteNotFoundException: Route "entity.node.import_form" does not exist. in Drupal\Core\Routing\RouteProvider->getRouteByName() (line 128 of /var/www/sites/datacenter.com/docroot/core/lib/Drupal/Core/Routing/RouteProvider.php).