No field code
Write
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: