Without DisplayFusion, when I maximize Firefox, I can flick my mouse to the very top edge of my monitor (the very top pixel) and click there to switch tabs to the Firefox tab that is under my mouse. You can also very easily slide along the top of the screen edge to move between tabs. (Fitt's Law describes this)

With DisplayFusion, I am using splits with no padding (basically the 3x1 preset), so the maximize button fills the split section entirely with my window. However, the top pixel of my Firefox window is the empty title bar,instead of the tab, so clicking on it just does what a blank title bar does (drag to move, etc), which does not switch tabs.

How can I use splits to divide up my ultrawide monitor into 3 screens, and still be able to switch tabs by clicking tabs along the very top pixel of the monitor?