There are a lot of assumptions here, as there usually are with all of us in almost everything.
1. What is trivia? To you it may be one thing. To me it may be something different. To
@Boris Badenov, it would almost certainly be a third thing.
2. Who cares about trivia, really? Trivia be damned! Right now we have a crisis of fundamentals. We have many "pilots" who literally don't know aerodynamics, and many more who know a little bit about aerodynamics, but only by rote for a test.
3. Sadly, the profound -which is almost always a simple statement or formula that explains the complex- comes from measuring and integrating and understanding the vastness of details. It is all too often that those details are viewed by the unengaged and uniformed as, yup...
trivial.
there, that's what trivia is.
for what constitutes "importance" or "value" - you could, actually, you know, use math to figure out what was "important" to know, because knowing it (and not being able to look it up) was important enough that failure to do so would kill the average dude or dudette flying... which, to circle back, is what AQP is supposed to be doing.
If you asked me what I thought constitutes "trivia" I'd define it by what is "not."
Trivia is things that failure to know does not fall into the following categories:
1. Not knowing it can result in death or injury.
2. Not knowing it can cause you to damage the airplane.
3. Not knowing it is *likely* to result in a violation or significant legal trouble.
4. Not knowing it is going to cause significant costs to the operator of the airplane.
Trivia would be like knowing the pressure of the oxygen bottle even though you have no gauge that displays it, you're not responsible for filling it, and you cannot change it.
Trivia would be like knowing that the engine driven fuel pump is 850PSI (or 1000PSI or 20PSI, the number doesn't matter) nominally or something when you have no gauge, or even if you do have a gauge depending on some contexts. Whereas knowing the unmarked temperatures on a gauge might be helpful if you could conceivably use it.
Trivia would be like, "knowing the exact stall speed of the airplane in knots" - you probably don't actually need to know that because it's going to change based on weight, AoA, etc. Furthermore, you can feel it anyway, and for more modern airplanes, there's like 25 ways the shaker can activate or an actual visual depiction of the appropriate angle of attack to fly and stall protection. I've memorized it for many airplanes, and you should be aware of generally where it's at, but if you say 70KIAS and it's 72KIAS, who cares? I can't fly that precisely anyway. Conversely, knowing the maximum operating weight and how to calculate it? Useful and important, even though it's a number.
Trivia would be like knowing the voltages on the various buses in the electrical system when you have no possible way to measure that in flight, or the maximum floor loading in the cabin.
Trivia is better defined by what it's not.
Is not knowing it going to kill you? No. Ok, will you break anything if you don't know it? No. Ok, will you get in trouble if you don't know it or otherwise embarrass yourself? No. Ok, is it going to cost a lot of money if you don't know this un-marked thing and you operate with disregard to it? No. Then it's trivia.