Created attachment 140030 [details] screenshot The blending mode combobox and opacity slider takes up a bit of vertical space. I was just thinking that if we reduce their height by even 1/3, there can be the extra space for displaying an extra layer (at the default thumbnail size).
Needs discussing with UI people. One could also argue that these frequently used elements need to be full size to make them easy to hit with a stylus.
You'd need to make custom widgets for that, because the spinbox and combobox widgets have a fixed by the widget style height.