Using ViewModels with UI hints WPF is a furious fast way to get your UI in place. However there was no declarative way to introduce splitters between UI parts.
There is now.
The EAInfo parts of Modlr is built with ViewModels and UI hints, and I can show you how to add splitters:
Right click in the ViewModel designer where you want the splitter:
Choose splitter kind and you are done.
I did this for the EAInfo ViewModels, and now you have a splitter between the grids and images and things.
If you want a different color width or style of your GridSplitters – define a Style for GridSplitter type…
(works in build 5580 and beyond)