Top Level Only?

If needed, I can extend Multicolumn Category Widget to display the hierarchy as well.

Yes, I need this function. Can you tell me what you need to do it? My site is https://www.metaldetectingdatabase.com. I want the Database tab and the Index tab to break into columns. The Database tab shows all the hierarchy. The Index tab only shows the child category. Let me know if you can do this.

I have to extend the backend to add an option if one wants an hierarchical category list (not everbody wants this) and the frontend code needs including the CSS to be changed as well, since get_category() is only used to fetch one level. This has to be extended, so the sub-categories get fetched and output as well.

However – since I’m really busy with other things at the moment I don’t have time to work on this before next week.

Well – I just had a look at what you want. Well – you want a category list inside a page. But a widget is not used for this. What you need as a plugin which provides a short code to output things withing a page or post.

Ok, but what short-code would I use? I can put it in the php right?

There is no short code yet and there are no plans yet to add a short code in the Multicolumn Category Widget. But you may use the “Widgets on pages” plugin to put the Multicolumn Category Widget inside a page:

https://www.ads-software.com/plugins/widgets-on-pages/

But since you just want to have a list inside a page, you just can add just the links to the category pages manually. I think this is way easier in your case.