Save & Edit button looks like two overlapping buttons

This issue can be fixed by turning off Integrate into dropbutton on Save & Edit settings.

+        if (
+          $entity->getEntityTypeId() === 'node'
+          && in_array($entity->bundle(), ['landing_page', 'page', 'article'])
+        ) {
+          $form['#attached']['library'][] = 'save_edit/save_edit_css';
+        }

We shouldn't be hardcoding content types here.

As mentioned in #11, unchecking "Integrate into Dropbutton" should fix the issue.

I have been looking into how to get content types to actually use a dropbutton, but it seems dropbuttons are no longer used for node edit forms. See #2914426: Revert the removal of the entity save dropbutton in Drupal 8.4.0 →

So the "Integrate into Dropbutton" configuration is supposed to support functionality that is no longer provided by Drupal core. I'm not sure if contributed modules may still convert the simple buttons back to a dropbutton though.

The best solution may be to update the default configuration for module installation to leave that checkbox unchecked and provide a note that dropbuttons are no longer used in Drupal core.

Created a new issue to address this, 📌 Remove Dropbutton support to resolve theming issues Fixed

Closing this issue as a duplicate.