Today I published in my GitHub repository a formatter class for abap2xlsx. The class offers six methods to format a range in an Excel spreadsheet. E.g. with the method set_border_outline_range you can set a border around a range. You must initialize the class with a zcl_excel object and optional with the number of the worksheet. Now you can set a border with the start and end column and row, as well as the border style and color. The other five methods offers the possibility to set the font size and color, the bold style, the background color of a cell and last but not least a grid border. These methods are a good pattern to build your own format methods for ranges of cells easily. I use the abap2xlsx method change_cell_style, which offers the possibility to change special attributes. Hope it is a good base for other abap2xlsx programmers.
Hint: This is an outdated post. The class is not longer available.