* Better and more complete use of C++ namespaces.
* Better use of C++ features. Especially standard library features as their implementation becomes more widely available. For example, we might be able to simplify some things in Octave by using the C++17 filesystem and special functions libraries, if they provide results that are at least as good what we are using now.
=== Eliminate C preprocessor macros where possible ===
=== GUI code editor ===