Seeing all open files in tabs

Firstly, apologies for the poor subject heading but I have no idea what to call this.

When I first installed my new X6 ages ago, I would automatically get tabs of all files I have open in the same way all open webpages are shown as tabs in my browser. I am sure I also had it in earlier versions of Corel. This is what it looks like in PhotoShop (the only example I can find since I no longer have any earlier version of Corel.)

tabs in menu

The only way I can see them now is to go Window/Cascade.

Now, I'm sure Corel still has this so can anyone tell me what I click to get it back?

Also, what is it actually called?

Thanks