Played around with this functionality a bit, looks like in order to keep groups separate, there has to be an ungrouped column in between, otherwise excel will just merge the groups. I created an extra column between my groups and used this to label the different groups while they were collapsed. Doesn't work exactly as I'd like, but it's functional. 

The first option is nonsense as it only collapses one column, only the - symbol is above column B and d but these columns do NOT collapse at all.

Agreed, this wasted a bunch of my time when I was almost fooled by it... until I collapsed my groups then I saw he had wasted my time

This DOES NOT work.... This ONLY groups ONE column... if you go to hide the selection it will only hide ONE column not the second as well... All you have done is group ONE column. To make it even worse, you then proceed to debunk your consecutive grouping attempts by going into detail on how the grouping actually works in that you seam to have to have a blank cell next to the range you want to group. muppet!