When you open a file (clicking on the Open File icon right above the SQL window), it always opens up a new tab. I liked it better when it just opened in the currently selected tab. I may open a file, run it to get the result, then need to open another file to run, then another. These are all just one-time runs, they don’t need to be on separate tabs. I already have enough tabs open with what I’m working on. If I need it in a new tab, I will open a new tab and then open a file.
If you click on the File menu (very top of screen), then Open File, it opens the file in the old SQL Editor (even though I am sitting in UE).