When you first take on the challenge of being a manager, you're likely to become so time-poor that coding will be an extremely low priority item on your to-do list. So, naturally, your coding time is likely to be next to zero, if not completely zero. If you expect and anticipate encountering this wall, then it will help, psychologically, to make your transition from a coder to a manager easier.
Expecting to keep up your coding and be an effective manager, certainly at the beginning, is ambitious at best, or foolish at worst.
One of the very first challenges you will face as a manager is figuring out how to divide your time: identifying which bush fires need to be put out first, and which you can let burn, let alone the fact that you'll need to be able to identify whether they are even genuine fires. In your new role, this translates to how to prioritize ...