I'm adding drug-development features, and polish to my open-source molecule viewer and editor, Molchanica: https://www.athanorlab.com/molchanica.

Source code, in rust: https://github.com/David-OConnor/molchanica I've split out its building blocks into their own libraries on crates.io, for anyone building other bio or chem software. I don't think anyone uses them at this time.