List identifier, what it is and uses

When I edit a list, I can change the list name, but there is also a list identifier box that is empty by default. What is this for? and how is an example of how to use it? (I wasn’t able to find this in the docs)

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It’s used to identify a task across all lists.

If set, the identifier is for example shown on the kanban board above the task title:

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