Unfortunately, it still doesn’t work, even on version 14.2. When I use {Center, Center}, it does center, but the vertical spacing between lines changes, disrupting the layout of the dataset.
Try this:
Dataset[ {<|"colA"->1,"colB"->2,"colC"->3|>,<|"colA"->4,"colB"->5,"colC"->6|>}, Alignment->{"colA"->Right,"colB"->{Center,Automatic},"colC"->{Center,Automatic}} ]
Well, I'm not entirely sure why, but Dataset seems to need both vertical and horizontal alignments to be specified. In the documentation, the default Alignment for Dataset is {Left,Baseline}. Maybe when you just set Alignment->Center all it does is replace Baseline with Center. I don't know. But anyway, if you use a pair for Alignment, the Dataset displays as expected. For example, try Alignment->{Center,Center}.
Dataset
Alignment
{Left,Baseline}
Alignment->Center
Baseline
Center
Alignment->{Center,Center}
