📄 theme.css

.wp-block-separator.has-css-opacity {
  opacity: 0.4;
}

.wp-block-separator {
  border: none;
  border-bottom: 2px solid currentColor;
  margin-left: auto;
  margin-right: auto;
}
.wp-block-separator.has-alpha-channel-opacity {
  opacity: initial;
}
.wp-block-separator:not(.is-style-wide):not(.is-style-dots) {
  width: 100px;
}
.wp-block-separator.has-background:not(.is-style-dots) {
  border-bottom: none;
  height: 1px;
}
.wp-block-separator.has-background:not(.is-style-wide):not(.is-style-dots) {
  height: 2px;
}