Prior to Backdrop 1.3.0, custom blocks configured under
admin/structure/block were stored in the
block_custom database table. In Backdrop 1.3.0 and later, the configuration of these blocks has been moved into configuration files. The switch to configuration files allows blocks to be moved across sites using the Configuration Management UI.
Although this change does not affect any APIs, the lack of the database table may affect code that is querying it directly. Rather than query the database table, if your module needs to get a list of custom blocks provided by block module, it is recommended that you use the block_block_info() function.
All API functions remain the same, with the exception that they store the block differently than before.