EasyCatalog can hilight the selecting fields in a document using a blue outline in a data panel as shown:
This is enabled via an “Advanced Preference”, available from the InDesign->Preferences->EasyCatalog dialog box. The Advanced button reveals the settings below:
Hilight Document Selection can be found in the Miscellaneous section and should be set to true. This change only takes effect once InDesign is relaunched.