1. First you need to upgrade to Drupal 9.4.4 or higher. For help with updates on Pantheon Composer driven sites, see Drupal on Pantheon (Build a site with Composer).
2. Update modules providing additional CKEditor 4 plugins to the latest release of the major version you're on.
3. Modules that have added CKEditor 5 support should provide support for both CKEditor 4 and 5, and provide an automated upgrade path (for toolbar items and plugin settings) from 4 to 5.

Enable the CKEditor 5 module

Leave CKEditor module enabled.

Convert text formats to use CKEditor 5

1. Go to Text Formats ⮕ Editors in the Drupal Configuration user interface (usually under admin/config/content/formats) and click Configure for each text format.
2. Under Text Editor change selection to CKEditor 5 and click Save configuration.
3. Text formats must be updated one at a time. This will automatically migrate your text format configuration to CKEditor 5.
4. Disable (old) CKEditor module.
   NOTE: This will change your configuration so make sure your export it