This module was proposed for Drupal 8.3.x and added as an experimental module.

The module is mentioned in An update on the Layout Initiative for Drupal 8.4/8.5. Drupal 8.5 also includes the related experiment module named Layout Builder that is effectively Panelizer in core

The module is in Drupal 8.5 marked as experimental. The code for 8.5 is on display at api.drupal.org/api/drupal/core!modules!field_layout!field_layout.module/8.5.x

The module applies predefined layouts to "entity displays", the old content type concept expanded across all entities. The field layout can be overridden on specific pages using Layout Builder.

The following text is the included help text. The help text then directs you to this page, the documentation page you are reading.

The Field Layout module allows you to arrange fields into regions on forms and displays of entities such as nodes and users.

Field Layout manages two separate layouts for entities, one for view and another for form displays.

When Field Layout is installed, Field Layout updates all entities to have view and form displays. If you uninstall Field Layout, Field Layout resets all entity displays to a default one column layout.

For each entity view mode, Form Layout adds a Layout ID. There is no editing or creation of the layouts. The layout control is in other modules. The layouts are found using Layout Discovery.

There are Twig files and CSS for layouts in the Layout Discovery modules. Layout Discovery also accepts layouts from other modules via several paths described in How to register layouts with Layout Plugin. Panelizer and similar modules can feed in layouts.