Is it possible to get a GridLine over a BartChart ?
Gridlines draw it under and Mesh does not seem to work with BarChart.
BarChart[{Range[10], Range[10]},
ChartLayout -> "Stacked",
GridLines -> {None, {4}},
GridLinesStyle -> Directive[Orange, Thick]]

This can be done via a method option:
(this should work for any graphic.)