ISO/IEC 27701, adopted in 2019, added additional ISO/IEC 27002 guidance for PII controllers.

Here is the relevant paragraph to article 48 GDPR:

7.5.1 Identify basis for PII transfer between jurisdictions

Control

The organization should identify and document the relevant basis for transfers of PII between jurisdictions.

Implementation guidance

PII transfer can be subject to legislation and/or regulation depending on the jurisdiction or international organization to which data is to be transferred (and from where it originates).