There’s no black and white answer, so I think you’re stuck, AngryGumball. But as an academic exercise, here’s my take on it:
An element is completely singular. Nothing more can really be subtracted from it.
A compact and unique “combination of elements” is a “trick”. It can be as compact as a Brain Twister, or longer Like the Skin the Gerbil (or Matrix, or any number of other named tricks you could mention). The defining characteristic is that subdividing it only produces elements, not more tricks. If you subdivide a Matrix, for example, you can find a Double-or-Nothing. But you don’t find a White Budda within.
If you create a unique combination of elements and transitions, you can call it a trick. But if you transition a Kwyjibo into a Spirit Bomb, you’ve just made a combo. As long as you can say with certainty that the combined elements don’t contain a pre-existing trick within… well, it’s a trick. Name it if that’s your thing! I also feel that no matter how unique, if you’re just chaining together elements in a way that drags on too long and doesn’t create anything interesting as a result… well, to me it might still be a “trick”, but it’s boring as heck and you shouldn’t probably want to take ownership of it. Keep working at it!
A combo is a combination of tricks. I think that’s the most “obvious” one. It’s clear in and of itself as a definition. The haze only comes in when you suspect that you’ve chained together some “known/named” sequences and you WANT to call it a trick but you secretly know that it’s not really.
I also don’t see any real problem with naming a combo. And then in video sections of sites if it ends up in a list of “tricks”, well… there aren’t any combo police trying to ruin your fun, are there?
Perhaps a better and more compact conclusion goes something like this: You get to decide. You do a “series of moves” that you feel is unique and that you’re proud of? Go ahead and call it a trick. And start adding it to your combos.