Correct. The conversion is available, but only in one direction—the leftmost regular column may be converted TO a header column, the topmost regular row may be converted TO a header row, to a maximum of five in each case.
For your situation (one header column that you want to replace with a regular column), you can do the whole table replacement described by Wayne, or you could replace only the single column:
- Click on any cell in column B to select it. Press option-left arrow to Add a Column before column B.
- Click on the Column A reference tab to Select the whole column. Copy.
- Click on cell B1 (in the new column B).
- Go Edit > Paste and Match Style.
- Click on any cell in column A.
- Go Table > Delete Column.
Works fine IF the table contains no formulas that referenced cells in column A. Any such formulas will now show a REF error, and will need to be reconstructed to correct the cell references to the new column A.
You can get past this issue by formatting any cells containing column A cll references as Text before deleting column A, then changing their format back to Automatic (or whatever setting you had previously) after column A is deleted.
Regards,
Barry