Here are 4 modules that provide enhanced linking within CKEditor. They have similar features, but do things in different ways.
CKEditor Entity Link
Provides a CKEditor button for creating links to internal content with a configurable autocomplete search.
https://www.drupal.org/project/ckeditor_entity_link
Linkit
Same as CKEditor Entity link, but without custom link attributes.
https://www.drupal.org/project/linkit
D8 Editor Advanced Link
Enhances existing CKEditor link button to configure link attributes.
https://www.drupal.org/project/editor_advanced_link
D8 Entity Editor Advanced Link (Linkit)
Adds Linkit widget to Entity Embed buttons.
https://www.drupal.org/project/entity_embed_linkit
Linky
Add links to content within an entity.
https://www.drupal.org/project/linky
Link Attributes
Enhances default link button to provide attributes. Also allows menu links to have attributes.
https://www.drupal.org/project/link_attributes
CKEditor Better Link
[deprecated?]
Enhances default link button to provide url, anchor, email options.
https://www.drupal.org/project/editor_better_link
Anchor Link
Anchor link plus attributes.