After using the Symbol On The Fly tool to insert a box symbol onto a page, how can the size of the box be changed?
Right-click the Symbol On The Fly box on the page.
Select Symbol Settings from the pop-up
In the Scale area of the Symbol Settings dialog, set the Horizontal value to the desired width and set the Vertical value to the desired height.
Since the connection points of a Symbol On The Fly are intended to fall within the border of the box, it is recommended to delete and re-insert connection points that are outside the box after the resizing operation.