The ToolBox closes itself, whenerver a block gets dragged out. This makes programming harder, because it has to be re-opened for every new block. I would appreciate to have an option to disable this feature, for example in the Settings -> User Interface Settings.
What do you propose to happen when you have finished dragging blocks from a selection ?
I would suggest that the selections stays open. To still make it possible to close, I'd maybe add a 'show less' button on the side.