The Jake Group

The plugin adds the option to change the color of the admin bar, as well as 
change the WordPress logo in the admin bar. It can also be used to customize 
the logo on the login screen, and to hide certain dashboard widgets. For 
developers, there are additional features such as a contact widget that can be 
added to the Dashboard. The developer features are only available to users who 
have access to edit their plugin files.

WP-Admin Customizer

Customize certain features and colors of the WordPress admin interface.

Felix Arntz

Introduces a simple method for defining block areas to use the block editor outside of the post content.
This is an experimental plugin that explores basic usage of Gutenberg blocks outside of the content bubble, on a sitewide level.
In the long term it will likely eliminate itself once WordPress core and Gutenberg will have completed the next phase of advancing to the sitewide level. The plugin exists as a baseline to have an easy way for experimenting with similar functionality already today.
<h4>Usage</h4>
After activating the plugin, you can create and edit block areas under Appearance > Block Areas. There should be two block areas already, <code>header</code> and <code>footer</code>.
Block areas are identified by their unique slug. Since <code>header</code> and <code>footer</code> are expected to exist, make sure not to delete them.
In order to print a specific block area, for example in your theme, use <code>block_areas()->render( $slug )</code> (e.g. <code>block_areas()->render( 'header' )</code>).
You can also explicitly add theme support, specifying which block area slugs your theme relies on (e.g. <code>add_theme_support( 'block-areas', 'header', 'footer' )</code>).

Block Areas

Great idea and reliable plugin, which we use to allow our clients to edit areas  using Gutenberg outside of the main content area.

Very simple yet very powerful

Introduces a simple method for defining block areas to use the block editor outside of the post content.

WP-Admin Customizer vs Block Areas