The global block within a Splunk SOAR playbook is primarily used to import external packages or define global variables that will be utilized across various parts of the playbook. This block sets the stage for the playbook by ensuring that all necessary libraries, modules, or predefined variables are available for use in subsequent actions, decision blocks, or custom code segments within the playbook. This practice promotes code reuse and efficiency, enabling more sophisticated and powerful playbook designs by leveraging external functionalities.