I assume by the "title bar" you mean the top border of the window where the filename is displayed. This just drags the window around, but the window of any file opened earlier is not visible behind it.

The problem isn't that the window occupies the whole screen, it's that the two files are effectively open in the same window, yet only one is visible at a time, without any kind of tabs to switch back and forth. And, even if there WERE tabs, it wouldn't help because I sometimes need to see several files simultaneously. Even minimizing the window to the taskbar doesn't show the other file. The earlier file IS open because when I close the more recently opened file, the other one is then visible again.

In the mean time I've re-done the work and have managed to turn off the coupled scrolling when using the "side by side" option. It's still clunky but at least doable.