水野史土

This plugin shows post/page/category/tag/comment/media/user IDs on admin’s edit post/page/category/tag/comment/media/user pages. You can see the ID when you visit an edit post/page/category/tag/comment/media/user page. 
Since this plugin hooks on ‘edit’ link, only users with priviledges can see IDs. For example, a user of author role can see post IDs, while a user of subscriber role cannot.
You can find a brief description in Japanese on a book <a href="https://php4wordpress.calculator.jp/" rel="nofollow ugc">Introduction to PHP for WordPress Users.</a> (written in Japanese.)

ShowID for Post/Page/Category/Tag/Comment

This plugin shows post/page/category/tag/comment/media/user IDs on admin's edit post/page/category/tag/comment/media/user pages.

ska-dev

websevendev

jimedwards

This plugin adds additional advanced inspector controls to Gutenberg blocks that allow to add any custom HTML attributes to the block’s front-end output. This allows you to add inline styles to fine-tune the block’s appearance, set aria attributes to improve your site’s accessibility, add data attributes to integrate with any JavaScript modules or even JavaScript DOM event attributes such as <code>onclick</code>, <code>onchange</code> or <code>onload</code>.
<a href="https://playground.wordpress.net/?plugin=attributes-for-blocks&url=%2Fwp-admin%2Fpost.php%3Fpost%3D2%26action%3Dedit" rel="nofollow ugc">Demo</a>

Attributes for Blocks

It's perfect for what I need! I hope you'll keep it updated as this behaviour should really be native in WordPress!

This should be native!

This is just Gold

Allows to add HTML attributes to Gutenberg blocks.

ShowID for Post/Page/Category/Tag/Comment vs Attributes for Blocks