How to use code/JavaScript fields?

[bookin]

I want to use JavaScript code in my Datasource/Connector but I am faced with two problems:

• the javascript code isn't highlighting. Fields open the editor in the popup but it is just a text editor.
• but the biggest problem - the text doesn't save to the datasource, when I re-open datasource or use export/objects API I don't see field with code that I saved

@Property(
            name = "someJsCode",
            title = "Some Script",
            description = "Some js function ",
            hints = {UIHints.CODE, UIHints.JAVASCRIPT}
    )
    @SchemaAnnotations.StringSchema
    String beforeRequestJSCode();

Do you have examples/explanations on how to use code fields?
Thanks

LucidWorks: 5.4.1
SDK: 4.0.0

[bookin]

2. New fields saves almost only if remove plugin and re-upload (sometimes works with an update, sometimes no)