Apologies for being cynical, but this is a question that has a relatively obvious answer.
If you need to improve in something, do more of it. For what it’s worth, if I want to get better at climbing. I drop my weight by a few kg for an event as it’s a logical given, climbing is easier with less weight.
I also massively build on my elevation by including big hills in my ride. Stopping at them, and doing repititions on them, then moving on.
Sorry bud, this is the answer. There is no magic bullet.