Make base fields configureable in form display

Problem/Motivation

Base fields are not configurable in the "Manage form display" tab. Especially when adding multiple fields to menus, then ordering those fields can greatly improve the editorial experience.

As a side effect, this also enables field widgets for base field. Especially it allows to use Linkit → for the menu links, which is a major improvement in UI and features (e.g. linking to Media entities). (Note: currently requires an extra patch for Linkit ✨ Linkit for Link field Fixed , but this patch is likely to be merged soon)

Proposed resolution

Just add

function hook_entity_base_field_info_alter() {
  $fields[$FIELDNAME]->setDisplayConfigurable('form', TRUE)
}

to every field and let Drupal core do its magic.