In a VFC add an interface operation (or select one with an interface already present)

With the VFC checked in, click on a row for a VFC operation.

The Edit operation window opens and it is possible to change e.g. description, uri etc. All values should be read only when the VFC is checked in

The new values are not immediately included in the generated TOSCA (as it is not re-generated when the status is checked in). However, if the VFC is then checked out, the new values entered when it was checked in are included in the newly generated TOSCA.