Final answer:
The correct environment variable for creating custom tags is DT_CUSTOM_TAGS, used for organizing resources in a computing environment.
Step-by-step explanation:
The environment variable used for creating custom tags for identifying and organizing resources in a computing environment is DT_CUSTOM_TAGS. This variable would be set to apply custom-defined tags which can help in managing the assets, particularly for filtering and categorization purposes in various applications, including monitoring and managing deployments.
For other context-specific metadata in computing environments, DT_PROCESS_METADATA could be used. However, the correct answer to the question is DT_CUSTOM_TAGS when specifically referring to the creation of custom tags for resources.