"Tab blocks" / Horizontal block editor

[DennisSnijder]

Whenever working with Blocks, you're always adding new blocks on the vertical axis. It would be nice to have blocks on the horizontal axis (Tabs, but editable) for adding / managing blocks.

Here's a mockup of what something like this would look like:

[tylandavis]

I would love a feature like this. Would be nice to have this for both Blocks and Arrays.