Submenu dropdown horizontal with multicolumns

Hi there,

I've tried to find a solution but found nothing.

This one here, is the solutions I'm looking for, but I want to group the elements.
https://generatepress.com/forums/topic/submenu-dropdown-change-from-vertical-to-horizontal/

change

1 menuitem
2 menuitem
3 menuitem
4 menuitem
5 menuitem
6 menuitem

to

1 menuitem 2 menuitem 3 menuitem
4 menuitem 5 menuitem 6 menuitem

Do you have any tip or an idea?

Thanks in advance!
Arndt