@SaucySigma For things like:
(∈ℝ)^2 >= 0,
∈ℝ + ∈ℝ ∈ ℝ (hence why I want the symbol above the set's name, not to its left)
But the thing I'm thinking about at the moment is pattern matching, where I want to write something like x^(∈ℤ) or x^(∈ℚ) for integer or rational powers of x