Make it possible to group a single column so it can be labeled similar to other groups that contain multiple columns. For example a table might have the following groups:
Unit 1 X vars
Unit 1 Y vars
Unit 2 X vars
Unit 2 Y vars
Unit 3 X vars
:Single Column that is a Unit 3 Y variable but has an unrelated name
Column groups are handy in tables with many columns. Making a group of target variables or columns related to a prediction make the tables easy to navigate, and grouping single columns would allow a user to use standard or logical group names regardless of the analysis size. It also might be beneficial to make groups with no columns, to be populated later.