First of all I'd like to thank the developer for such a feature rich extension.
I've created a testing map, category, popup style, map type, place marker group and place marker, but can't seem to make the place marker display tabs, although I've defined two of them and set them to replace the default content of the popup.
In the attached screenshots you can see the relevant settings.
Add Popup content => it is for adding "popup content" - in your case "Title and desctiption" and "Addition HTML text into tabs (as first or last tab).
If you set it to "replace content" - your tabs will not be displayed, only content.
But styles for popup will be applied.
It was ported from my Google's extension, when you can use different popup types - default infowin or infobubble, and infobubble has its own style.
As for OSM - you can control style, and can add content to first or last tab.
In your definition (replace content) it is the same as Action by Click = "Open Popup", because you replace content.