No field code

Adds new watchers to an issue. This virtual field can also be used to add new watchers to linked issues, sub-tasks or issues returned by JQL easily without replacing or removing an existing one.

Alternatively you can use the Watchers field with the additional + prefix. 

The main use case for this virtual field is to add a watcher through the Update fields post function or the Update field action.

To learn more about this writable field, check the following use cases:

• Add watcher depending on security level
• Automatically become watcher of every issue blocking an issue assigned to you.