Nested archivable dictionaries

Hello
I am trying to save data to document user data. In effect I ended up with 4 levels of nested archivable dictionaries.
dict1
dict2
dict2.1
dict2.1.1
dict2.1.2
dict2.2
dict2.3
dict3
dict3.1
dict3.2
Is it possible to manipulate (read, write, add, delete) entries in deepest level (lets say dict2.1.2) or do I have to make a copy and then replace the whole dict2?