Place Blocks overview

The Place Blocks module allows you to place blocks from every page, except for Administration pages.  You can initiate a Place Block workflow by the clicking on the Toolbar item.  Once active all regions in the theme will show the "plus sign" button at the top of each region.

Clicking the button will bring up the block modal selection UI.  There you can choose which block instance to use and set it's configuration options.  Block placement is specific to each theme on your site, as per the Block API.

This module is included in Drupal 8 core since Drupal 8.2 It was marked as hidden since Drupal 8.4, deprecated in Drupal 8.8.0 and finally removed in Drupal 9.