About 40 years ago, someone came up with the theory that plant-based proteins were incomplete and that vegetarians had to eat “complementary proteins” during the same meal, for example, rice and beans, or tofu and sesame seeds. This fallacy was refuted decades ago, but the myth persists.
It turns out our body maintains pools of free amino acids that it can use to do all the complementing for us. Some 90 grams of protein are dumped into the digestive tract every day from our own body to get broken back down and reassembled, and so our body can mix and match amino acids to whatever proportions we need.
Plant-based eaters do not need to be concerned about amino acid imbalances from plant proteins. For more information, see this video on Nutritionfacts.org.