substance/packages/blockquote/_blockquote.css

Substance is a JavaScript library for web-based content editing. It provides building blocks for realizing custom text editors and web-based publishing systems.

.sc-blockquote {
  border-left: 2px solid var(--border-color);
  padding-left: 30px;
}

.sc-switch-text-type .se-option.sm-blockquote {
  border-left: 2px solid var(--border-color);
}