You can add layers at any time using the New Layer command on the Layers panel menu or the New Layer button at the bottom of the Layers panel. The number of layers a document can have is limited only by the RAM available to InDesign.
To create a new layer at the top of the Layers panel list, click the New Layer button.
To create a new layer above the selected layer, hold down Ctrl (Windows) or Command (Mac OS) as you click the New Layer button.