Copy functions between home and CAS

[retoa]

x and capital X are for the prime (and also for the user) two different variables with two different values.
If it would convert it automatically then you would loose the value stored in X (CAS->home) or in x (home->CAS).
So I don't think it is a very good idea. Better doing a substitution, so you can decide which variable to use. You can also pass a function f(a) to F1(X) changing 'a' to 'X', on the fly it would always change x to X, a to A and in the plot app you can not plot a function wit 'A' as argument.

The "on the fly" method would be fast, but not flexible.