Currently Gutenberg does not display the Custom Fields meta box. Before Gutenberg, in WordPress 4.9 and earlier, the “Edit” screens in the WP Admin Area optionally displayed the Custom Fields meta box. The Custom Fields meta box is employed by millions of sites, themes and plugins. Including my own collection of WordPress plugins, which use custom fields for Posts, Pages, and many Custom Post Types. Basically Custom Fields are a critical part of WordPress functionality, so I wrote a plugin that “brings back” Custom Fields on Gutenberg-enabled sites: Custom Fields for Gutenberg.
Custom Fields for Gutenberg
I’m not gonna say too much more about it than that. I think it’s pretty self-explanatory. At this point anyway. Eventually I will be building out the plugin with additional Gutenberg features, anything cool related to Custom Fields and such. Currently, Custom Fields for Gutenberg does one thing and does it well:
Display Custom Fields on Gutenberg-enabled screens
The plugin includes some default options to disable custom-field display on any particular post type(s). And you can specify any custom fields that should not be included in the Custom Fields meta box. Plus some other options to fine-tune how the custom fields are displayed. Check out the screenshots below for more details.
Here are a couple of screenshots to give you a better idea. Click on the thumbnails below to view full-size version.
For more information, list of features, and FREE download, visit Custom Fields for Gutenberg at the WP Plugin Directory: