ds-site/Configuration/RTE/Default.yaml

# Load default processing options
imports:
  - {resource: "EXT:rte_ckeditor/Configuration/RTE/Processing.yaml"}
  - {resource: "EXT:rte_ckeditor/Configuration/RTE/Editor/Base.yaml"}

editor:
  config:

    # Ensure that special characters are not converted to HTML entities
    style:
      definitions:
        - {name: "Inline Code", element: "code", classes: ['']}

    heading:
      options:
        - {model: 'paragraph', title: 'Paragraph'}
        - {model: 'formatted', view: 'pre', title: 'Code Block'}

    toolbar:
      items:
        - bold
        - italic
        - underline
        - strikethrough
        - subscript
        - superscript
        - '|'
        - removeFormat
        - '|'
        - bulletedList
        - numberedList
        - '|'
        - indent
        - outdent
        - '|'
        - blockQuote
        - '|'
        - link
        - '-'
        - style
        - heading
        - '-'
        - sourceEditing

    importModules:
      - '@typo3/rte-ckeditor/plugin/typo3-link.js'

  externalPlugins:
    typo3link: {route: "rteckeditor_wizard_browse_links"}

processing:
  allowAttributes: []
  HTMLparser_db:
    tags:
      ol:
        allowedAttribs: []
      ul:
        allowedAttribs: []
      code:
        allowedAttribs: []
      pre:
        allowedAttribs: []
  allowTagsOutside:
    - pre
    - blockquote
    - ul
    - ol
    - li
    - br