The outside-in approach

There is an experimental module in Drupal 8.2 that allows you to editing blocks and other site configuration from the frontend of the website, just like Quick Edit for content. To enable this, install the Settings Tray module.

When you browse the Drupal site, you will note a new Edit button in the left of the toolbar. Clicking on this will allow you to edit blocks and the site configuration.

For more information, review the Drupal.org handbook for this feature at https://www.drupal.org/docs/8/core/modules/outside-in/overview.