Built-In Button

val browseExtension = ExtendableTextComponent.Extension.create(
    AllIcons.General.OpenDisk,
    AllIcons.General.OpenDiskHover,
    "Open file",
    { System.out.println("Browse file clicked") }
)
val extComboBox = ComboBox<String>(STRING_VALUES)
extComboBox.setEditable(true)
extComboBox.setEditor(object : BasicComboBoxEditor() {
  override fun createEditorComponent(): JTextField {
    val ecbEditor = ExtendableTextField()
    ecbEditor.addExtension(browseExtension)
    ecbEditor.setBorder(null)
    return ecbEditor
  }
})

ExtendableTextComponent.Extension browseExtension =
  ExtendableTextComponent.Extension.create(
    AllIcons.General.OpenDisk,
    AllIcons.General.OpenDiskHover,
    "Open file",
    () -> System.out.println("Browse file clicked")
  );
ComboBox<String> extComboBox = new ComboBox<>(STRING_VALUES);
extComboBox.setEditable(true);
extComboBox.setEditor(new BasicComboBoxEditor() {
  @Override
  protected JTextField createEditorComponent() {
    ExtendableTextField ecbEditor = new ExtendableTextField();
    ecbEditor.addExtension(browseExtension);
    ecbEditor.setBorder(null);
    return ecbEditor;
  }
});