[Theme Horse Support Team]

Hi @sjoerd,

Our theme supports all most all the Gutenberg Blocks, and WordPress generally updates the Blocks time to time, so adding/setting the table header is the new update by the WordPress and we even update our theme time to time also based on it. So Thank you for helping us identifying about the issue that we missed to update. We will be including these on our next Theme Update soon. For now please go to ‘Appearance > Customize > Additonal CSS’ and paste the below Custom CSS code.

.wp-block-table tr th {
	padding: 5px 10px;
	border-style: solid;
	border-width: 0 1px 1px 0;
	border-color: rgba(0, 0, 0, 0.3);
}

You can make the table align center from the text align option of the respective table and there is no option for setting the ‘th’ tag only background color instead you can set background color for whole table. If you want to set background color for seperate ‘th’ tag only then you can add background color property on above code.
like:-
background-color: yellow;

Thanks