The runscript command allows running a Python script (.py) or ChimeraX command script (.cxc) with file pathname script and any needed command-line arguments. Substituting the word browse for the pathname brings up a file browser window for choosing the name and location of the script interactively. The arguments are passed to the Python script as sys.argv, sys.argv, etc., or substituted into the ChimeraX command script for $1, $2, etc. The --script startup option calls this command.
See also: alias, open and its forEachFile option