In a daily standup, the project lead sees a senior developer reassigning easy backlog items to others, saying seniors should focus on complex tasks. What should the project lead do?

The sprint retrospective is the appropriate forum for discussing team process improvements and addressing issues like task assignment practices. It's a dedicated event for the team to inspect how the last sprint went regarding individuals, interactions, processes, and tools, and to create a plan for improvements. Discussing it in the retrospective allows for open dialogue and collective problem-solving. Raising it in the sprint review is incorrect because the review focuses on the increment and adapting the product backlog, not team processes. Telling the senior developer to stop is premature and doesn't address the underlying issue or involve the team in finding a solution. Supporting the senior developer's actions is incorrect as it bypasses a potential process issue that could impact team dynamics and efficiency.