Makoto

Low-Key ToolBar makes the block editor toolbar less noticeable and improve block editor UX.
I think block editor toolbar is useful, but too big and too conspicuous and disturbing. 
Sure, top toolbar mode is not disturbing, but is not user-friendly.
This plugin add its own setting sidebar to block editor and You can control scale, opacity, vertical position of the block editor toolbar.
By adjusting these properteis, the toolbar will be less noticeable, and it will improve UX.

Low-Key ToolBar

This plugin makes the block editor toolbar less noticeable and improve block editor UX. You can control Scale, Opacity, Vertical Position of the block …

Marcel Bootsman

Auto Hide Admin Bar makes the WordPress Toolbar disappear – and reappear when hovering the mouse pointer over the top of the browser window. 
You end up with a clean view of your site, and keep having access to the WordPress Toolbar. 
If you have any comments or questions, please use the <a href="https://wordpress.org/support/plugin/auto-hide-admin-bar" rel="ugc">support forum</a>.

Auto Hide Admin Bar

This plugin adds an auto-hide feature to the WordPress Admin Bar or Toolbar.

Low-Key ToolBar vs Auto Hide Admin Bar