Preview to show Thumbnails by default on PDF
Just upgraded my iMac from El Capitan to High Sierra. Before the upgrade I used to be able to select and open multiple PDF files at once and Preview would display it all within a single window, side bar would show all the thumbnails on the left and I could scroll up and down through 20-30 different documents with ease. Now I get all of them on separate tabs instead which is exactly the reason why I preferred Preview over Adobe Reader. I can obviously change it to thumbnail once opened but it always default back to the way I don't want. I've been through Preferences for Preview but there's not much in it, is there any way to change the default view?
Thanks in advance.
iMac with Retina 5K display, macOS High Sierra (10.13.4)