Balancing functionality and simplicity in a GUI for digital art tools involves:

1. User research: Understand artists' workflows, needs, and pain points.

2. Prioritize features: Focus on essential tools and features, hiding advanced options.

3. Intuitive design: Use clear icons, labels, and layouts to reduce cognitive load.

4. Contextual tools: Display tools and options only when relevant to the current task.

5. Customization: Allow artists to personalize the interface to their preferences.

6. Progressive disclosure: Gradually reveal advanced features as users become more familiar.

7. Streamlined workflows: Optimize toolsets and menus for common tasks.

8. Visual hierarchy: Organize elements by importance, using size, color, and position.

9. Feedback and guidance: Provide subtle hints, tutorials, and tooltips.

10. Testing and iteration: Refine the GUI based on user feedback and testing.

11. Consistency: Establish a consistent design language throughout the application.

12. Flexibility: Allow for multiple workflows and artistic styles.

By striking a balance between functionality and simplicity, the GUI empowers digital artists to focus on their creative work while still providing the necessary tools and features to bring their vision to life.