This 1 mindset will increase your vert immediately: try to approach your jump like a max effort speed-based exercise! Imagine going for a squat PR, now with the same intensity, use all your effort into a single jump and do it as quick as possible like the explosive start of a sprint into a jump. It's like getting into the zone for a second, leave all other variables out and now your only goal is to sprint to near the target, perform a perfect penultimate step without slowing, and transfer all that momentum upward. Another tip I can give you is to inhale sharply and hold your breath like you are doing an anaerobic exercise that requires a burst of strength in a short amount of time. Now try these tips out yourself!