Some synonyms that you can use for the word "well-composed" include poised, harmonious, balanced, ordered, methodical, structured, and organized. Poised is a word that suggests calmness and controlled behavior, making it an appropriate alternative for a person who is well-composed. Meanwhile, harmonious and balanced describe an object or piece of work that's pleasing to the senses, either because of its symmetry or the congruity of its parts. Methodical, structured, and organized, on the other hand, describe a process or plan that has a systematic and well-defined approach, allowing for a smooth execution. These synonyms are interchangeable with well-composed and can be used to give a more varied and nuanced description.