iPad OS 26 unwanted changes

iPadOS multitasking has received a significant makeover from that to which you may be accustomed in earier versions of iPadOS. You would be well advised to review the official iPadOS User Guide and the many available online tutorials (such as YouTube) to become better acquainted with the new multitasking interface and associated gestures and controls.

Work with multiple windows at once on iPad - Apple Support

OS - iPadOS 26 - Apple

Be aware that the previous Slide Over view has been retired, but Split View remains - although it is accessed differently. When using Windowed Apps (as illustrated in your screenshot) key to controlling the windows is the traffic-light icon - one tap to activate, then tap the red button to close the window, yellow to minimise and green to maximise the window to full screen.

Touch-and-hold the traffic-light icon to access other windowing options; you can have two or three App windows side-by-side - or a spit the screen into four quadrants.

If an App window is already maximised, swipe downwards from the top-edge of the screen to expose the new menu bar - then use the traffic-light icon as described above.

As indicated by sberman, you can change multitasking modes in iPad settings:

Settings > Multitasking & Gestures - select Full Screen Apps or Windowed Apps

[Edited by Moderator]

Try Settings > Multitasking and Gestures > Full Screen Apps.

You appear to have Windowed Apps chosen instead.