Nested compilation presents us with two issues.
The code must be fenced in by some naming convention.
Then if the code has a name, that name must be filled in somewhere
but this tangles up the dictionary mechanism.
A notation for anonymous code pieces is comparatively easy to accomplish and can be found in about denotations.
The more difficult part is the subject of this lecture (forthcoming). In the meantime you may study the word NESTED-COMPILATION in the ciforth library.