Drupal - Unable to install the XYZ module since it requires the A module

Adding the yaml_editor to core.extension.yml solved the issue. It perhaps were removed due to a complex git merge, and that's why my install process started to fail all that sudden.

I had the same issue. My situation as follow

Custom module with configuration. On export, the module's configuration data exported with name match the the code(php) configuration name as (xxx.settings.yml). If the "xxx" doesn't match the module name, the error occurs.

I changed the configuration name in the source code and it's working fine.

Suggestions:

• Try partial import by: drush config-import --partial.

• Make sure the required/missing module is present in core.extension.yml, e.g.

  module:
    missing_module: 0
  

  Note: If you're using Configuration Split module, make sure to populate the module to all files.

• Make sure you've run drush updb and cleared cache (drush cr).

• Try exporting first (especially core.extension.yml), then import again.
• Try to Synchronize from the UI (at /admin/config/development/configuration).

Drupal Console

As for the alternative approach, try to do config import using Drupal Console, sometimes it can give you more clues about what's wrong. E.g.

drupal config:import

Or for a single item or a file (--file), try:

drupal config:import:single