How do I add multiple headers in a journal table?

I'm trying to edit the D&D 5e Compendium equipment tables to add additional options for my players and adjust setting prices. Those tables have multiple headers, as shown with "Item," "Ammunition," and "Arcane Focus" in the screenshot here . I'd like to be able to group certain sets of new items in the same table, as with all the other item groups in that table, using additional header-style rows. It's obviously possible because it exists – it's there in that screenshot – but I cannot find user controls that allow you to do so. Can anyone help me out?

The simple answer is: the tools for making the compendium have other options.  The potential solution is: build the table how you want it to look in Google Docs, then copy paste it into the handout, it should retain the formatting.  The obnoxius answer is: if all else fails, you can manually edit the html source of the handout textarea to add the HTML you need to get the look you want. You’ll need to understand the browser Developer Tools, HTML and CSS, and once you add the manual changes, change one more bit of text through the editor to make sure it knows you’ve changed something and click save.