Chaining extension parameters

Hi Gregory,

I built my first extension (a base64 file encoder) and I wonder if it is possible to achieve my goal with the current state of the framework:

I have defined two arguments for my function - one is of type file and the other is of type text.

I would like to be able to specify as value for the second field either another environment variable or the result of another extension.

Is this possible to do currently ? Maybe I am missing a parameter ?

Thank you in advance for the feedback !