kollapsminoriteten/wp-includes/blocks/rss/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;
}