### What problem does this PR solve?
Feat: The query variables of the subsequent operators can reference the
structured variables defined in the agent operator. #10866
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
### What problem does this PR solve?
Feat: Add VariablePickerMenuPlugin to select variables in the prompt
text box by menu #4764
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
