We've been using CiviCRM (now on v5.55.2) installed on Drupal (now v7.92) for several years. During that time we've used a couple of different rich text editors (TinyMCE, FCKEditor, CKEditor) and IMCE as a file manager to create and edit content in Drupal with good success. We've not had a need for a rich text editor in CiviCRM in the past but recently we decided to start using CiviMail to send newsletters to our members.
In an effort to configure CiviCRM with an editor I've carefully read the page, "Configuring CiviCRM to use Default Drupal Editor" in the System Administrator Guide and confirmed that everything is set up as that document describes. Unfortunately, the Default Drupal Editor option does not appear in the drop down list of possible editors for the CiviCRM WYSIWYG editor setting and nothing I've tried makes it show up.
I have searched high and low in this forum for clues about what may be wrong but haven't found the exact problem. There is one thread that is close but their problem was in using system-flow templates. We are using User-driven message templates.
Since the last question related to this feature was posted in 2018 I can't help but wonder if the feature is still available. Any ideas would be greatly appreciated.