'Executive presence' is vague on purpose, usually because the person giving you the feedback hasn't broken it down themselves. It's not a personality trait and it's not something you either have or don't. It's three learnable skills, and you can work on each one separately.
The first is conclusion-first presenting. Executives are trained to hear the answer before the reasoning. If you walk through your analysis chronologically and arrive at the recommendation at the end, you'll lose the room before you get there. State the recommendation first, then back into the reasoning only as far as the room wants to go.
The second is storytelling, meaning the ability to give a number or a decision a context a non-specialist can hold onto. 'Defects dropped 12 percent' is a fact. 'We used to get three complaint calls a week on this line, now we get one a month' is the same fact with a handle on it. Executives remember the handle.
The third is composure under questioning. This one is mostly mechanical too. When someone challenges you in a meeting, mirror their question back before answering it, and take a breath before you speak. That pause reads as control, not hesitation. People who seem to have executive presence usually aren't calmer people, they've just built the pause into their habits.
Work on these three separately and the vague feedback stops being vague. None of it requires becoming a different person.
"Executive presence" breaks down into three mechanical, learnable skills rather than a personality you either have or lack.