I'm just going to leave this one here. The Gutenberg UI for dealing with post metadata is horrid. I wait on each release to address this awful shortcoming. No satisfaction yet.

I'm not a developer but I know enough php and jQuery to have created some really useful metadata boxes for our organizations website. Sure the traditional php based metaboxes are still there but without refreshes, it's very difficult to see if the action hooks are still firing the way they used to. Several of the metaboxes I developed use dynamically developed options for select controls and/or autocomplete from an AJAX data source. Used to take me 5 lines of server side code to render a second editor to save fully HTML formatted metadata. Try that now in Gutenberg.

Maybe I'm not the target demographic but my metadata is as important, maybe even more important than the post content. WordPress went from slightly awkward but robust for post metadata and took many steps backwards to the current Gutenberg UI for metadata. Gutenberg might be terrific for post content but it's an epic regression for dealing with post metadata in my opinion.