@stray77 is correct about training early. Many say top after the 5th node (pair of leaves) appears. Some say pinching earlier is better because she heals faster.
I recommend you follow @Silky_smooth on Insta and growdiaries.com. She’s a cannabis plant whisperer. She teaches to mainline and flux plants so they deliver more flower than you’ve ever grown, and in a shorter plant. No need for extra height. She also knows methods to increase THC and terpenoid production.
Her methods are advanced, proven but easy to follow.