QT Designer is the WSWIG editor that comes with PythonQT for designing UIs. You can then either use the ui which gets saved or exported (as a python .UI file) directly calling it in your python code, or you can translate the UI code with a command that converts into straight python code.
It is fairly standard for UI building in the CG industry for Tools and Plugins for apps like Maya or Houdini, Katana, etc.
Is it possible to export XD UIs in a similar useable manner? I ask because QT designer has big limitations and is really hard to work with from a designer perspective.