Defining Line Ends
From LibreOffice Help
You can define any object to be included in the list of available line ends.
- Use the draw functions to create an object to be used as a line end.
- Select the object and choose Format - 'When in Writer: Drawing Object - 'When in Calc: Graphic - Line.
- In the dialog, click the Arrow Styles.
- Click Add and assign a name to the new arrow style.
- Click OK to close the dialog.