In the Data Sheet window, when trying to split a column with the Split tool in the window header, the default names for the Left and Right columns do not display correctly in the pane.
The Left and Right name columns are blank - actually they are invisible.
Dragging the cursor from right to left will show that the name is there but it is reversed - white type on a light blue background. You can triple click in the name field and type in the name of your choosing but it will also be reversed.
Clicking the Split button in the pane will successfully split the column and the left and right column names in the pane will be new columns in the Data Sheet.