There are no secrets to improve the vertical jump. It is actually fairly simple but if you are not naturally explosive it can take some Time to reprogram the nervous system.
1) do jumps daily, not at a super high volume, overdoing jump volume is actually a good way to become less explosive. No more than 5-10 min doing sets of ni more than 5 reps.
2) loaded jumps (barbell jump squats for example) are also a very good tool to use, but most people use way to much weight; the goal is not to see the heaviest weight you can jump with, but how explosive you can be with added weight. Most people should use 20-30% of their Max squats.
3) become very explosive in the whole power spectrum; jumps, jump squats with 20-30%, speed squats with 40-50% sometimes with added chains, olympic lifts with 70-80%
4) use depth jumps for 2-3 weeks, 20 total jumps twice per week for a rapid peaking. But only use it when you improved all elements in 3) because depth jumps only work for 3 weeks and only once in a 12 weeks cycke