CSIS has something called an "issues management brief". I don't know why the acronym is IMU, but it's been described as an issues management note.
I've had a number of different jobs and I may have seen such things in my reading packs over the years. None of them, to the best of my knowledge, has ever been directed to me. That's not the nature of the role of the national security and intelligence adviser, and certainly not of the other roles I have occupied over the past number of years.
I'm assuming that if CSIS has such a thing as an IMU for information, it might have an IMU for action, but that would be a question best put to CSIS representatives.