I have also noticed that, waiting for an LLM answer makes my mind wander to completely unrelated topics.

What I've found useful is to create a tasks.md file where each bullet point / task is one implementation. Bullet points that belong together and can be done in the same chat session are grouped together.

I easily enter a flow state during writing these detailed implementation plans. Then I can also start multiple chat sessions for parts that don't interfere with each other, while I'm waiting for an LLM answer for one part I can get started on the next or start reviewing one of the previous answers.

I have also explored more complex, e.g. using Kanban board for tasks, but I found great value in these simple yet effective setups.