Junior-level imposter syndrome looks like "I don't know what I'm doing." Senior+ imposter syndrome looks like something subtler: "I know what I'm doing in my specific corner, but everyone else here is operating at a higher level."
The shift from "I'm not good enough" to "I'm good enough but they're better" is its own trap, and it gets worse as you climb. A few patterns that show up at staff/principal/director levels: You attribute your wins to context ("the team carried it," "I got lucky with timing") and your losses to character ("I just don't think strategically enough"). You over-prepare for meetings where you're the most experienced person in the room, because you're convinced someone will discover you don't deserve the seat. You compare your internal experience (uncertainty, false starts, anxious moments) to other people's external presentation (confident, polished, decisive) and conclude you're behind. You read peer-published think-pieces and feel intellectually outclassed, even though those think-pieces are weeks of editing condensed into something that reads like effortless brilliance.
The high-leverage reframe: at senior levels, calibrated uncertainty is the skill. The people who project total confidence are usually wrong more often than the people who admit doubt, they just don't notice. Your ability to say "I'm not sure" without panic IS the senior trait, not the bug.
Practical exercise: next week, in three different settings, say out loud "I don't know yet, but here's how I'd find out." Notice that nothing bad happens. Notice that the room often respects it more than the alternative.