I used solution from this topic How to have custom nested configuration App.Config nodes and section. But I need a possibility to change values in custom section’s properties from code. Now I have “System.Configuration.ConfigurationErrorsException: ‘The configuration is read only.'” error on setter of properties like this

    [ConfigurationProperty("ChartName", IsRequired = true)]
    public string ChartName
        get => (string)this[nameof(ChartName)];
        set => this[nameof(ChartName)] = value;