Unique ID
A unique ID, also called item ID, identifies each item. It consists of a project key, a set key, and a set counter. Unique IDs remain the same even if the item name or content is changed. They can't be edited or duplicated.
Project key — Identifies which project an item belongs to. Project keys must be unique to each project, and must be 1–16 characters long, consisting of letters, numbers, and underscores. A project or organization admin can change the project key, but that doesn't reset the numbering of items.
Set key — Identifies item sets for each project. You can use the same set key across sets or projects. Project or organization admins can change a set key to better meet your organization's needs.
Set counter — A number automatically added to the item. Unlike the global ID counter, you can reset the set counter when you change the set key.
You can use the set key across multiple sets of the same item type. However, be aware that the set counter is shared across all items using the same set key.