Provide a way to use different values for the target attribute for the title if the Link checkbox is enabled

Makes much sense. The states value is hard coded though to node_title which shouldn't as the field is also used for user, taxonomy, media fields, so we need to figure out something else here. Removing the #states in the patch is fine for me as well, we could always add a description explaining that the target only works when the link checkbox is enabled.

Hi swentel
Thanks for the code review.

I have debugged the code and found that we can use the plugin_settings_edit option from the form state storage as it contains the current field name.
See Drupal\field_ui\Form\EntityDisplayFormBase::multistepSubmit().

Also, I fixed the hardcoded field name in states on line 31 in the Title.php

yes, awesome, merged, will come in release somewhere next week, thanks!