Preview suddenly opening in tabs no matter what!

I sure hope someone can help because I'm at my wits end.

All of a sudden in the past couple of weeks my Mac (Ventura) is opening pdfs, etc in Preview in TABS. I have NEVER used tabs, do not want tabs, and in fact 90% of my job all day is comparing things that need to have numerous windows open at the same time.

I have quit & restarted Preview

I have shut down and restarted my Mac

I am running the latest install of Ventura 13.6.6

I have Preview Settings set to "Open each file in its own window"

I have Mac System Settings>Desktop & Dock>Windows & Apps set to NEVER under Prefer Tabs when opening document

What is a person to do?!

Now today it is suddenly not adding them in Tabs, but into what looks like the side bar BUT ISN'T!!!!!!!!!!!!!! If I try and drag one out of the fake sidebar onto the desktop it duplicates it, adds a 2 to the name and puts THAT in the fake sidebar (!)

If I show Thumbnails, it only shows the one document that should actually be shown in the Thumbnails column (which to me IS the "sidebar" - and you still then see to the right of that all these same weird separate documents piled into a pretend "sidebar" - what the heck is happening!!!!!

Why on earth would this behavior suddenly start 2-3 weeks ago? I can only think it had to do with an update???

I'm attaching a screenshot of this.

Even weirder, if I bother to right-click the single icon and choose Open, it opens as an individual document. But who has time to have to right-click instead of double-clicking or having Automator do it???

I just want and need to have my Preview files open in separate windows always always always.

Thanks!

With the "Thumnails" opened it looks like this: