Under Material Refresh (assuming LtR language), the open a new tab + button is all the way over on the right, when new tabs open on the left.  This distance can be really big on high resolution monitors.

I almost always use keyboard shortcuts to open new tabs, but I just want to open one with the mouse and it took me an embarrassingly long amount of time find that + button.  This is exacerbated when there's only one tab active in a window, since there's no visual clue that tabs are even a thing.