[Design] Redesign add block to notebook experience

Created by: marisak

Container epic for design work related to the "add block to notebook" experience.

The current design/interaction patterns for adding a block to a notebook are very influenced by DeepNote. This may not be the best pattern for us in the long term. I envision this work as including, at the very least: (A) Exploration of other interaction patterns, (B) Feedback gathering, possibly via a working prototype, (C) Visual changes.

Issues related to exploration of other interaction patterns:

• Change action menu for blocks

Issues related to feedback gathering:

• (none created yet)

Issues related to visual changes:

• Redesign file block display
• Redesign search query block
• Compute block for notebooks

User flows: Create notebook; Edit notebook