Hello  I tried this,

Notebook 1 :

dbutils.jobs.taskValues.set(key = "my_key", value = "hi From Notebook1")

Notebook2:

X = dbutils.jobs.taskValues.get(taskKey="01", key="my_key", debugValue = "Fail")

print(X)

 Here I get "Fail" as output, its not fetching my_key