Dear Professor, I hope this message finds you well. I am currently engaged in machine learning research using ChimeraX. As part of my work, I need to substitute various groups on the phosphorus atom, including methyl, tert-butyl, cyano groups, and others. However, the current substitution function does not cover many groups, so I have been manually adding them to the SEQCROW library. At present, I am building the structures in Gaussian, which is quite cumbersome. Since I am not very familiar with ChimeraX, I am unsure whether it allows for manual molecular structure building. If such functionality is available, it would greatly assist my work. I would greatly appreciate any guidance or suggestions you might have. Thank you very much for your time and assistance. Best regards, Youcai Zhu 化工化工 1366924572@qq.com