You can use
np.split
and np.where
to do thisnp.vstack(np.split(lst, np.where(np.array(lst) == 'A')[0][1:]))[:,1:]
Output:array([['', '3', '4'],
['', '0', '2020/07/25 10:13:23'],
['3', '2', '2020/07/25 10:13:29']], dtype='<U19')