Function set_string_at 

pub fn set_string_at(
    strings: &mut Table,
    key_path: &str,
    value: Value,
) -> Result<(), ManifestError>

Set value at a dot-separated key_path in a [strings] tree, creating intermediate tables as needed (the write half of set-string). Errors on an empty path segment or a path that traverses an existing non-table leaf.