If you don't like the appearance of a shape or text box when you add it to your file, you can format the shape or text box, and then designate it as the new default format for that open file. After that, any new shapes or text boxes use that formatting.
But remember, these steps only set defaults for the file you have open—the spreadsheet, slide presentation, email message, or document. To set defaults for all files you can create a template
Change defaults for shapes and text boxes
Excel, Outlook, Word, and PowerPoint
Select the shape or text box.
Right-click the border of the shape or text box and click Set as default on the shortcut menu.
When you add a shape to that file, it uses the formatting you applied.