When plotting values inside segments on a combo chart it would ideal for me to show the values inside bars vertically and values on lines horizontally. As per the screen shot there only seems to be the option to do one or the other to all expressions regardless of whether they are displayed as bars or lines. I'm assuming, therefore, that there's no way around this but if anyone has any ideas please let me know!
Yes, that's a global option and it's either vertical or not. A workaround for this is to use two charts which are overlapping eachother and where you adjust various layout-settings especially hiding titlles, borders ... and so on respectively making them transparent per option or expression argb(0,0,0,0).