OK, so this was very easy. I added an extra option to show both History and Categories (Groups), or just one of them. I decided to not make an option to show them next to each other, for that would again fix the possibilities. Now it is possible to have the layout you want. So if you want to show the History and Categories next to each other, you could make two <div>-sections and use the code snippet twice, once for the categories only and once for the history only.
Snippet works as follows:
page_id => the news page you want to generate the menu from
date_option => 0:=summarize according posted date (default), 1:=summarize according published date
group_header => header above the group menu (default: '<h1>Categories</h1>')
history_header => header above the group menu (default: '<h1>History</h1>')
display_option =>0:=show both history and categories (default); 1:=show only history; 2:=show only categories
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