Nested Grid blocks - show only one grid visualizer at a time

[talldan]

What problem does this address?

At the moment when a grid is nested in another grid, the overlaid visualizer components look visually confusing:

What is your proposed solution?

Adding some rules about which visualizer or visualizer cells are shown based on the block selection should solve this issue. Something along these lines:

• When the parent grid is selected (or a child of that parent that doesn't have its own grid), don’t show the visualizer for the child grid
• When the child grid is selected don’t show the parent visualizer cells that are behind the child grid