Preview.app on 10.14 - print all open PDF documents

My Mac used to have 10.11 and I would open a folder full of PDF files with Preview. Each is a single page PDF for an envelope. They would all open in a single window with thumbnails on the left for each file.

I could then print them all with a single print dialog. This was very easy and fast.

Now, with 10.14, when I open the same group of PDFs, they open in individual windows and I have to go through print dialogs for each one.

I can choose 'Window > Merge All Windows', which doesn't always merge them all, but still printing gives me a dialog per each open file and I can't find a way to print them all at once.

Any ideas?