Originally Posted by Guessed

Every template contains a bunch of Table styles. One of those table styles is set as the default table style that is used when you create a new table in the document.

You will need to firstly identify which table style is your default and change the settings on that table style. You can do this by inserting a table and then looking to see what table style is applied to it.

Now modify that Table style so:
- Apply formatting to: Whole table, then Format>Table Properties>Table Tab>Options and set your margins
- Apply formatting to: Header row, then Format>Table Properties>Row Tab>Repeat as header row at the top of each page = Tick

Note that the Apply formatting to is the key selection in all of this. If you don't pay attention to this context for your change, you run the risk of the table styles becoming very complex.