Yes. I'm not sure I'm fully on top of Reactions either.
The UI isn't exactly stellar at the moment. This is general, and it applies to reactions as well.
In addition, I think Larian hasn't fully decided how they would translate Reactions from the TT rules to their video games. So the mechanism isn't fully figured out yet. At least, that's what they said in the pre-EA communication, and we haven't had much update about where they are and where they are going since EA started. So, to my understanding, this mechanism is still likely to evolve.
And finally, I'm fully with you : the game is currently not very good at teaching us how to play it. Hopefully, the explicit in-game tutorials will improve, the UI will do a better job at implicitly teaching us the rules, and there will be an in-game manual so we can actually read the rules, as Larian will have eventually made them. But that will only be when the game (and the rules) are much closer to completion.