Actually I started to develop Guietta exactly because using the QT GUI builder (Qt designer) was often too time consuming for simple applications.
Designer works great for GUIs with complex layouts. Having an intermediate XML representation puts a lot of distance between your code and your GUI. Sometimes this is good, other times is not. I rant a bit about this at the start of the introduction: https://guietta.readthedocs.io/en/latest/intro.html
I like the concept. I spent nearly a decade with Visual Basic, and got sick of building GUI's on the screen. It was a lot of repetitive manual labor when I didn't all that much care what my layouts looked like. Most of my programs are for limited use -- glorified scripts. I'd rather just sling a few lines of code and have it generate an ugly but functional layout for me.
1) tools like Delphi, VisualBasic (the classic version, not .net), and to some extent, HyperCard
2) GUI builders, which were popularized by Visual C++
#1 doesn't have (visible) layers or abstractions. It's a different way to represent your program. You place a few controls, tie them to actions (code), and that's your system.
#2 is like onions, with lots of messy layers, and tend to be way more cumbersome to deal with than the code itself.
I don't know of modern-day graphical programming systems. I haven't kept up with Delphi, but people who have claim the last useful version is Version 7 from 2002. After that, it went through some messy transition.
There is one GUI builder in Java I forgot the name, a plugin for Eclipse from Google, that allows to build GUI by drag and drop and jump into the code. It works directly by reading and writing any java code file, there are no extra files and layers of abstraction. It could understand Swing, SWT and a couple other major UI frameworks.
That's the only thing I know that's really seamless like old times.
It's been a while (I've never done autolayout and up) but I found Xcode Interface Builder to work in the fashion you describe. Probably not an accident as it descends from NeXT devtools which inspired e.g. VB (not sure about Delphi).
How well would these tools have worked with source control? Interface builder effectively uses XML files, but they are not meant to be edited/understood by humans. This effectively hides a layer of the "onion", but it makes it tricky to follow changes checked into VCS...
radio buttons still basically unsupported - no way of grouping them.
Add optional astropy units for values, maybe extending the tuple syntax: ('__a__', u.km). More difficult than it seems, because one needs to parse input strings. But very useful in a scientific environment.
'with' syntax still very limited, in particular locals() and globals() refer to the Gui class scope so for example anything imported at the beginning of the script is not available inside the with block.
Unit tests almost completely missing, also I have no idea how to properly test GUI code.
Designer works great for GUIs with complex layouts. Having an intermediate XML representation puts a lot of distance between your code and your GUI. Sometimes this is good, other times is not. I rant a bit about this at the start of the introduction: https://guietta.readthedocs.io/en/latest/intro.html