Nested grids demo

This example shows v5.x dragging between nested grids (dark yellow) and parent grid (bright yellow.)
Use v9.2 sizeToContent:true on first subgrid item parent to grow/shrink as needed, while leaving leaf green items unchanged.
Uses v3.1 API to load the entire nested grid from JSON.
Nested grids uses v5 column:'auto' to keep items same size during resize.

Add Widget Add Widget Grid1 Add Widget Grid2 entire save/re-create: Save Destroy Create partial save/load: Save list Save no content Clear Load