I googled my problem before I made this thread and found this guide, if you CTRL+F "stack" the picture shown has a little box for how many items you want to use. Has this been removed or something?

Also, on a somewhat related note, is it illegal to use Razer macros on this game? I've just been playing about and it turns out I can fully synth an item repeatedly with correct positioning of the mouse and a continuous macro that press "E" every 7 seconds.