こんにちは
下記 CSS ではどうでしょうか?
.wp-block-image.is-resized {
display: block;
}
.wp-block-image .components-resizable-box__container {
max-width: 100% !important;
}
.wp-block-image.is-resized > figcaption {
display: block;
}
もしかしたら、!important が必要かも
functions.php に記述する場合の例:
if ( is_admin() ) {
function fukidashi_enqueue_block_editor_assets() {
$style = <<<STYLE
.wp-block-image.is-resized {
display: block;
}
.wp-block-image .components-resizable-box__container {
max-width: 100% !important;
}
.wp-block-image.is-resized > figcaption {
display: block;
}
STYLE;
wp_add_inline_style( 'wp-edit-blocks', $style );
}
add_action( 'enqueue_block_editor_assets', 'fukidashi_enqueue_block_editor_assets' );
}