What makes a setup “HIGH PROBABILITY” to you?
It's a term I associate mostly with win-rates, really - so in itself it has only limited relevance to me, as part of a bigger probabilistic/statistical picture (the "highest
win-rate set-ups" are what
most people mean by "highest probability set-ups", and they're not often going to be the ones I'd want to trade, myself).
That said, and to answer your question, what makes a set-up "high probability" to me is always current, valid, statistical evidence that its win-rate is higher than whatever it's being compared with (which may or may not also make it more profitable).
For myself, I more or less ignore fundamentals unless I've been specifically notified of their likely relevance to me (that's easy for me to say as a fast-moving intraday trader, of course!), so it would be "technicals", really. Certainly including strong levels of support and resistance, when there are some. And I generally consider the most frequently touched/rejected and the most recently touched/rejected levels of previous support and resistance to have higher-than-average chances of becoming short-term future levels of support and resistance. For what it's worth.
In view of the way you've asked your question, I suspect that Marcel Link's book
High Probability Trading might interest you. It's not bad at all, as these things go. His principle contention is that similarity of patterns (whether price action or indicator-based)
across multiple time-frames makes for "high probability set-ups". I don't use time-frames, myself, but I used to and I know what he means and he's right. But - again -
don't make the mistake of imagining that the highest win-rate trades are necessarily also going to be the most profitable or indeed the best (judged by any other parameters) to trade. Would that it were that simple!