I thought you mean the extruder control on top which is already a dropdown.
Why would you need to control the temperature of unused extruder so often that it gets impractical to use the extruder accordion where you can set all extruders at once. I mean it s not that we do not have the control. But for normal printing I use none of them. When I need them then for manual control and there I have all on the right side as well.