Dashboard layout is tricky and doesn't let you do such manipulations in easy way. The reason is that even beginner level user will get layout done without any coding. It is powerful enough to rearange groups for different screen sizes with again - no special treatments or coding skills needed. Great stuff.
But that is only one type of layout and zero options.
To make it behave somehow different it takes to overwrite all that behavior and write your own layout rules. It is possible but takes at least intermediate CSS skills.
See this thread, you may find some ideas..
