Hopefully this isn’t OOT. A Sketch plugin, maybe can be a reference for Subform’s layout engine. Still kinda buggy though. It’s surprisingly easy to use.
Auto Layout for Sketch
David
#3
We tested the plugin extensively now in our design team and came to the conclusion, that it offers no unique benefit over the default sketch constraints. The positioning options seem more precise then they are in practice. There are still a lot of bugs with percentage widths influencing child elements weirdly. It works well for the demo stuff they show, but in a real world project it quickly becomes a nuisance.
Sketch itself offers no way to make layout flow possible. All you can do at the lowest level is absolute positioning and somewhat relative positioning when you start to cascade elements into groups. Sketch is (sadly) only a drawing app. Responsive reflow and elements influencing each other will take them a lot of engineering effort, which I'm not sure will happen.
But more tools and plugins tackling these problems brings competition, which in turn is great for us designers 
What would you say is the unique selling proposition of Subform?