Hi,

SaveStateCrossPages should work if the ID of the menu is the same on both pages, and it works best if you have the slide menu in a master page. You can also take a look of the following properties:

http://www.essentialobjects.com/ViewDoc.aspx?t=EO.Web.BaseNavigator.AutoSelectSource.html
http://www.essentialobjects.com/ViewDoc.aspx?t=EO.Web.BaseNavigator.AutoSelectTarget.html

Set AutoSelectSource to "NavigateUrl" will automatically select the item whose NavigateUrl matches the current page Url. In that case you don't need SaveStateCrossPages.

Back to your original question. Your question is actually two questions:

1. How to get the expanded menu group index?
2. How to save that index to a cookie?

To answer the first question, you would do something like this:

var index = e.getItem().getIndex();

You can find the related reference documentation at here:
http://www.essentialobjects.com/ViewDoc.aspx?t=JSDoc.Public.NavigatorEventInfo.html
http://www.essentialobjects.com/ViewDoc.aspx?t=JSDoc.Public.NavigationItem.html

There are also other methods you can use, such as getId, getPath, etc.

For the second question, you can find more information at here:

http://www.w3schools.com/js/js_cookies.asp

Once you've gotten value, saved it, you may still need to read it and set the expanded state back. To set the expanded state, set a top level menu item to selected, for example:

SlideMenu1.getTopGroup().getItemByIndex(your_saved_index).setSelected(true);

Let us know if you have any other questions.

Thanks