Eclipse Set Style Range not working as expected

We've developed a plugin that retrieves data from a third-party API and inserts it into the editor. We need to apply specific styling to the inserted content, which should persist until the user performs the next action (e.g., pressing a key).

Currently, the text insertion and initial styling application work correctly. However, the style is immediately removed.

Code:

    public Object execute(ExecutionEvent event) throws ExecutionException {
        
        IEditorPart editor = PlatformUI.getWorkbench().getActiveWorkbenchWindow().getActivePage().getActiveEditor();

        if (!(editor instanceof ITextEditor))
            return null;

        try {
            final ITextEditor textEditor = (ITextEditor) editor;
            final IDocument document = textEditor.getDocumentProvider().getDocument(textEditor.getEditorInput());

            final ITextViewer iTextViewer = (ITextViewer) textEditor.getAdapter(ITextViewer.class);
            if (iTextViewer == null) {
                return null;
            }

            styledText = iTextViewer.getTextWidget();
            int insertPosition = styledText.getCaretOffset();


            RestPayload job = new RestPayload();
            job.addJobChangeListener(new JobChangeAdapter() {
                @Override
                public void done(IJobChangeEvent event) {
                    if (event.getResult() != null) {
                        IStatus result = event.getResult();
                        Display.getDefault().asyncExec(() -> {
                            if (result.isOK()) {

                                try {
                                    String generatedCode = job.getPayload();
                                    document.replace(insertPosition, 0, generatedCode);
                                    suggestionStyle = new StyleRange();
                                    suggestionStyle.start = insertPosition;
                                    suggestionStyle.foreground = new Color(Display.getDefault(), 192, 192, 192);
                                    suggestionStyle.length = generatedCode.length();
                                    styledText.setStyleRange(suggestionStyle);
                                    styledText.update();

                                    Display.getDefault().timerExec(2000, () -> {
                                        styledText.setStyleRange(suggestionStyle);
                                        styledText.redraw();

                                    }); 

                                } catch (Exception ex) {
                                    logger.warn("Error inserting/styling code", ex);
                                }
                            } else {
                                showAlert("Code Assist Error", "Code assist failed: " + result.getMessage());
                            }
                        });
                    }
                }
            });

            job.schedule();

        } catch (Throwable eGenThrowable) {
            showAlert("Issue", eGenThrowable.getMessage());
            eGenThrowable.printStackTrace();
            logger.warn("Issue while exchanging data", eGenThrowable);
        }

        return styledText;
    }                                   

Note:

                                    Display.getDefault().timerExec(1000, () -> {
                                        styledText.setStyleRange(suggestionStyle);
                                        styledText.redraw();

                                    }); 

The above code snippet obscures the inserted code. However, it is not an applicable solution.