When using the Jet Table Builder, you have the option to save a template of the table you are creating. This template can then be re-opened later, should you wish to edit the structure of your table.
Editing Tables with the Jet Table Builder
When a table is created with the Table Builder, you are presented with the option to save a template of the design of that table:
Once that is done, you can go back into the Table Builder, select Open from the File menu…
… navigate to where the template was saved, and open it…
The Table Builder will then display the same information as was saved earlier and it is now available for editing: