The Light Control buttons are a depreciated feature since HDR Light Studio (8 Drop 1).
Light Control buttons have been replaced with keyboard shortcuts to LightPaint modes that can be used in the Render Views and Canvas.
We are leaving the information below for users of older versions of HDR Light Studio.
The Light Controls panel contains 'click, hold and drag' buttons to edit the size, rotation and brightness of a light. This provides an easy to use alternative to using the sliders to control these properties.
Keyboard qualifiers can be used to change the sensitivity of the Light Control buttons whilst dragging.
CTRL + Hold Drag = slower increment (i.e. smaller adjustment for distance dragged).
SHIFT + Hold Drag = faster increment (i.e. larger adjustment for distance dragged).