You need a custom editor stylesheet. Enqueue it with
add_action( 'enqueue_block_editor_assets', function() {
wp_enqueue_style( 'my-block-editor-styles', get_stylesheet_directory_uri() . "/block-editor.css", false, '1.0', 'all' );
} );
if your stylesheet resides in your theme’s folder. The above code can go in your theme’s functions.php. You might also need
add_theme_support('editor-styles');
if it’s not there already.
In block-editor.css, include
.is-selected {
border: solid 1px black;
}
I’d also find this feature helpful.
Sorry that I’m not so well versed in the technical details yet. What’s a “custom editor stylesheet”? And are you supposed to create block-editor.css as a new file? Where to put it?
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Could the feature maybe be included as an option there by default in the next WP version? To enable by clicking a checkbox? That would be aaaawesome. 🙂
