How can I navigate my transition from SDE3 to SDM?

Not directly related to how you can transform better.

But as an IC, and have seen this happen multiple time, keep in mind that you don't do what you were upset when your managers did.

• Listen to feedback from your reports.
• Understand that your words can deeply affect their lives, so act accordingly.
• Make sure you treat everyone fairly, explain your decisions about assignments to not have speculations.
• Defend them strongly, give them early hints about their performance, don't surprise them in the last minute.
• And, the most important one, have empathy and care, without it, your just another manager to add some posts about in Blind.