Get the model selected in the model navigator
To get the model selected in the model navigator, use the SelectedItems property of the INavigator object.
public void GetSelectedModelsByNavigator(ICommandContext c, ICommandParams p)
{
    IEditorPage editorPage = c.App.Window.EditorPage;
    if (editorPage.ActiveNavigator != "Model")
    {
        c.App.Window.UI.ShowMessageBox("Please switch to the model navigator before executing.");
        return;
    }
    //Get the models selected in the model navigator
    var selectedModels = editorPage.CurrentNavigator.SelectedItems.OfType<IModel>();
    foreach (IModel model in selectedModels)
    {
        c.App.Output.WriteLine("sample", $"Model: {model.Name}");
    }
}