Это один подход с использованием простой итерации.
Пример:
s = """TASK000123-Tomcat server hosted on tbu.test1 is down-P1 --In Progress
TASK000123-Tomcat server hosted on tbu.test1 is down-P1 --Completed"""
result = [["TaskID","Priority","Status"]]
for i in s.splitlines():
val = i.split("-") #Split by '-'
result.append([val[0], val[2], val[-1]])
print(result)
Вывод:
[['TaskID', 'Priority', 'Status'],
['TASK000123', 'P1 ', 'In Progress'],
['TASK000123', 'P1 ', 'Completed']]