Onboarding new users in complex GUIs poses several challenges:

1. Information overload: Users can feel overwhelmed by the sheer amount of features and options.

2. Steep learning curve: Complex GUIs require significant time and effort to learn.

3. Cognitive load: Users must process and understand complex information, leading to mental fatigue.

4. Navigation difficulties: Users may struggle to find what they need amidst complex menus and workflows.

5. Feature discovery: Users may not discover essential features or functionality.

6. User frustration: Complexity can lead to frustration, causing users to abandon the GUI.

7. High support requests: Complex GUIs often generate more support requests and tickets.

8. Difficulty in creating effective tutorials: Complex GUIs make it challenging to design effective tutorials or guides.

9. Balancing flexibility and simplicity: Complex GUIs often strive to offer flexibility, but risk sacrificing simplicity.

10. User segmentation: Different user groups may require tailored onboarding experiences.

11. Constant evolution: Complex GUIs often evolve rapidly, requiring continuous updates to onboarding processes.

12. Measuring success: It can be challenging to measure the effectiveness of onboarding in complex GUIs.

To overcome these challenges, consider using techniques like progressive disclosure, interactive tutorials, clear documentation, and user feedback mechanisms to create a more effective and user-friendly onboarding experience.