Is it possible to manipulate the PDF Bookmarks setup via ExtendScript

Thank you for your reply @frameexpert,

With your explanation and with the help of Save PDF with Bookmarks i got it to work as I wanted.

We have a CHP paragraf format that is not included in the PDF Bookmarks by default when we create PDF document. I now ensure that in a functions that closes all open files in the script.

Function is here to inspire others

function CloseAll()
{
    doc=app.FirstOpenDoc
    while(doc.id !=0)
    {
        var params = GetSaveDefaultParams();
        var returnParamsp = new PropVals();

        doc2=doc.NextOpenDocInSession;
        
        // Ensure CHP is included in the PDF Bookmarks
        var pgfFmt = doc.GetNamedPgfFmt ("CHP");
        if(pgfFmt.ObjectValid() == true) {
           pgfFmt.AcrobatLevel = 1;
           doc.PDFBookmark = true;
        } else {
            FmLogFile.writeln("Could not get CHP format");
        }
        
        doc.Save( doc.Name, params, returnParamsp);
        doc.Close(Constants.FF_CLOSE_MODIFIED);
        doc = doc2;   
   }

    book=app.FirstOpenBook
    while(book.id !=0)
    {
        var params = GetSaveDefaultParams();
        var returnParamsp = new PropVals();

        book2=book.NextOpenBookInSession;
        book.Save( book.Name, params, returnParamsp);
        book.Close(Constants.FF_CLOSE_MODIFIED);
        book=book2
    }
}