I've been searching around and looking into the documentation, but I'm not sure how to activate filtering via the column drop down the way you have it in normal grid panels.
I've tried to implement the ux.Grid.FilterFeatures but when I apply it to the tree panel, my panel doesn't render properly (all blue panel). I thought it might have something to do with its deferred layout, but when I do a treegrid.hide()/treegrid.show()/treegrid.doLayout(), it doesn't make a difference.
Has anyone gotten the filter feature working with the treepanel? Or has anyone got any suggestions on how to rectify this problem?
Tree stores don't have a filtering function, but I had to create one for an earlier project. Here's an example.
So, as a suggestion you could create your own filter drop menus using Ext.grid.header.Container configs in the tree columns (as covered here in the docs) these could be set-up to call some kind of filter function on the treestore like the one I linked to above.