After some research it seems that the filter widget is not retaining the options after closing.
Here is the pertinent portion of the script. It worked in 4.9.5 and 4.10
//get sales order number
var pItem = _list.currentItem();
var _so=pItem.rawValue(“lshist_ordernumber”)
var _pos=_so.lastIndexOf("-")
var _so = _so.substring(3,_pos)
//get cohead_id for this sales order
var result = toolbox.executeQuery(“select getcoheadid(’” + _so + “’)”);
result.first();
var _soid=result.value(0);
var params = new Object;
params.cohead_id=_soid
var wnd = toolbox.openWindow(“dspSalesHistory”, 0, Qt.NonModal, Qt.Window);
toolbox.lastWindow().set(params);
toolbox.lastWindow().sFillList();
setting the filter widget manually on that display and closing the display, the setting was not retained
adding the following to the script before the sFillList() made it work consistently.
toolbox.lastWindow().parameterWidget().applyDefaultFilterSet();