First is important to note that we do not recommend creating such a register.
Please note that ISO 27001 requires you to define a communication process, although there is no requirement that such a process must be documented.
Considering that, communication is an activity that is performed by many processes in information security according to ISO 27001, with different purposes. So, to have a centralized communication procedure would create an overhead for people responsible for communication with activities that may not be a part of their regular tasks.
That’s the reason there isn’t a specific template for clause 7.4.
The main documents in Conformio that define how communication needs to be done are:
the Information Security Policy
the Training Module
the Incident Management Procedure
the Disaster Recovery Plan
Additionally, most of the communication an organization performs is already registered through emails, Slack messages, etc. - so those can act as “registers”.
If you do want to create a separate Communication plan, then this article will provide you with further explanation about communication plan: