jQuery Grid Plugin - jqGrid

I use the treegrid adjacency model and am very happy. But with logn trees, there a wish to collapse/expand some nodes and remember individual state for each user e.g. in the cookie. Is there any way to do this with js? 

My Idea was to do it with php and send an ajax request to the server and save it each time some node is expanded ode colapsed, so I can take this information by creating a json by reload the grid. But maybe there are some easear way?