Populating multifield in page component dialog

Hello,

We have a requirement to pre-populate the multifield input field. The value will be used in page header section.

The value prepopluated will be something like this:

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When even the page property dialog is opened the value should be populated. Author can modify the value later any point of time.

Please let me know how this can be achieved ?

Thanks in advance.

- Meenakshi