Speaking as a web UI dev, I think I’d be more comfortable learning C++ properly than trying to maintain non-trivial UI with Blueprints. Is there even an API in place for this yet or is it just too messy to try to do it with code currently?
C++ UMG is called Slate, that should be enough to get you where you need.
My C++ Slate Wiki Tutorials
Here are my Slate tutorials, these are all pure C++
Creating a File Browser using Slate
Edit Text Widget With Custom Appearance
Fancy Custom SButtons