[Feature request] Simplify keyboard shortcut combo components

### Description

The current keyboard shortcut combo components are over-engineered and could benefit from a rebuild. This covers two related improvements:

- **Rebuild the keyboard shortcut combos** in a simpler, more maintainable way.
- **Replace instance-swap properties** for keyboard shortcut components with nested instance drop-downs, which are easier to use in Figma.

### Why

The current implementation has more complexity than needed, making the components harder to maintain and harder for users to configure.

Start by inspecting the existing keyboard shortcut combo components and their instance-swap properties in the Figma library. Rebuild the combos with simpler structure and replace the instance-swap properties with nested instance drop-downs; done means the components are easier to maintain and configure in Figma.

索引モデルが issue の本文から書いたものです。