📄 editor.css

.wp-block-rss li a > div {
  display: inline;
}

.wp-block-rss__placeholder-form .wp-block-rss__placeholder-input {
  flex: 1 1 auto;
}

.wp-block-rss .wp-block-rss {
  all: inherit;
  margin: 0;
  padding: 0;
}