Mary Rose Elbambo

BlockGlow adds a “BlockGlow — Custom CSS” panel to the inspector of every block. Use it to scope custom CSS to a single block instance. The plugin stores CSS in the uploads folder (under uploads/blockglow/) and enqueues the generated CSS file when rendering on the front end. If the uploads directory isn’t writable or file write fails, BlockGlow will fall back to outputting inline styles.
Key features:
<ul>
<li>Adds two block attributes to every block: <code>blockglowCustomCSS</code> and <code>blockglowId</code>.</li>
<li>Inspector panel with a CodeMirror-backed code editor (if WordPress provides it) or a fallback textarea supporting Tab and Shift+Tab outdent.</li>
<li>Live preview inside the block editor: custom CSS is scoped to the block in the editor so you can see the effect while editing.</li>
<li>CSS files are saved to <code>wp-content/uploads/blockglow/blockglow-<id>.css</code> and enqueued on the front end as a linked stylesheet; files are removed automatically when you clear the Custom CSS field.</li>
<li>Graceful fallback to inline styles when file writing isn’t possible.</li>
</ul>
How scoping works:
BlockGlow creates a unique <code>blockglowId</code> for each block instance and scopes your CSS with a wrapper selector like:
<pre><code>[data-blockglow-id="bg-xxxxxxx"] { /* your declarations */ }
</code></pre>
For convenience you can use <code>&</code> as the wrapper shorthand in the editor. Example:
<pre><code>& .my-class { color: red; }
</code></pre>
The plugin will replace <code>&</code> with the wrapper selector for both editor preview and front-end output.
<h3>Support</h3>
If you find issues or want improvements (for example: limiting who can edit per-block CSS, collecting styles into a single head include, or adding an admin UI to manage generated CSS files), open an issue in the repository or reply here and I will assist.

BlockGlow — Per-block Custom CSS

Adds a "Custom CSS" inspector panel to every Gutenberg block and saves per-block CSS files to uploads for front-end enqueuing.

iamaliiraja

Super Block CSS allows you to add custom CSS to your Blocks straight from the Block Editor (Gutenberg). It adds a syntax-highlighted CSS Editor where you can add additional CSS to your Gutenberg Blocks to style them the way you want.
Key features:
<ul>
<li>Adds a Custom CSS panel to every Gutenberg blocks</li>
<li>Syntax-highlighted CSS editor for easy coding</li>
<li>Apply custom styles to individual blocks</li>
<li>Global CSS option for site-wide styles</li>
<li>Real-time preview of your custom styles in the editor</li>
<li>Easy-to-use interface integrated into the Gutenberg editor</li>
</ul>
Whether you’re a developer looking to fine-tune your blocks or a site owner wanting to add some custom flair, Super Block CSS gives you the power to customize your Gutenberg blocks with ease.

Super Blocks CSS – Custom CSS for Gutenberg Blocks

Awesome plugin, i will always use this one from now.



WOW !!

Add custom CSS to your Gutenberg blocks directly from the block editor.

BlockGlow — Per-block Custom CSS vs Super Blocks CSS – Custom CSS for Gutenberg Blocks