yarn add @editorjs/text-variant-tune

import EditorJS from '@editorjs/editorjs';
import TextVariantTune from '@editorjs/text-variant-tune';
/**
 * Editor.js configuration
 */
const editor = new EditorJS({
  /**
   * Connect tool
   */
  tools: {
    textVariant: TextVariantTune
  },
  /**
   * Apply to all the blocks
   */
  tunes: ['textVariant'],
  // ...
})

import EditorJS from '@editorjs/editorjs';
import TextVariantTune from '@editorjs/text-variant-tune';
/**
 * Editor.js configuration
 */
const editor = new EditorJS({
  tools: {
    textVariant: TextVariantTune,
    paragraph: { // apply only for the 'paragraph' tool
      tunes: ['textVariant'],
    }
  },
})