WordPress/wp-includes/blocks/search/editor.css

.wp-block[data-align=center] .wp-block-search .wp-block-search__inside-wrapper{
  margin:auto;
}

.wp-block-search .wp-block-search__button{
  align-items:center;
  border-radius:initial;
  display:flex;
  height:auto;
  justify-content:center;
}
.wp-block-search__components-button-group{
  margin-top:10px;
}