In the wp-admin pages > Settings > Permalinks users can create custom URL structures for permalinks and archives.
This sounds great, but I'd rather accomplish this by manually editing my htaccess file (since it's already quite complex) instead of changing any Permalink settings in WordPress--which appear to simply modify my existing htaccess file.
Are there any changes made internally to WordPress when the Permalink settings are changed from the Default? If so, what changes are made?
Is it possible to keep the Default Permalink settings and configure a custom URL structure using htaccess only?