Then export another layer in the same window- and you get a new url with the same id - 2722. Opening the same url again and you will see the new layer you exported - which has deleted the previouse layer exported.
A way around this is to delete /#maps/2722 from the url and load the page again, but when you have alot of layers to export this is takes along time.
Go to http://suite.opengeo.org/geoexplorer/composer, click explort a map and you get a url that ends with eg #maps/2722. Open this url in a new window and it shows the layer you have stored. The url of the window you are in also changes to http://suite.opengeo.org/geoexplorer/composer/#maps/2722
Then export another layer in the same window- and you get a new url with the same id - 2722. Opening the same url again and you will see the new layer you exported - which has deleted the previouse layer exported.
A way around this is to delete /#maps/2722 from the url and load the page again, but when you have alot of layers to export this is takes along time.