Hi Claudia,
Actually, a "truly blank document" would be an empty canvas, containing no table of any type, no document header or footer locations, no document margins, no page definitions, no page orientation. Just a blank sheet onto which you could put whatever objects you wish.
Perhaps Apple should have named the 'not blank' templates "Basic" rather than blank, removed the header column, and left the header row intact. That would match the "Basic" table style available in the Tables button's menu, used for adding a table to a Sheet.
If you really do want to always start with a table which has no header rows and no header columns, it's easy enough to set up.
- Open a new 'blank' document (Apple's 'blank').
- Click on the Table 1 icon in the Sheets list and press delete. (faster than selecting cell A1, then taking two trips to the Table menu to delete first the (header) row then the (header) column)
- Click the Tables button and choose Plain to insert a 'plain' table (no header row, no header column)
- (optional) Add or delete rows or columns to make the blank table the size you desire.
- (optional) Position the table where you want it.
- Save the result as a Template.
- In Numbers Preferences > General > For New Documents, select Use Template, then Choose your new template.
Until you change that preference, any New document you make will contain your new, 'blank' table.
Regards,
Barry