On testing our app we noticed the application window causes memory leaks every time it is resized.

In the attached video you may find the behaviour of the default Qt Quick 2 application window: at the beginning, the application occupies 10-11 MB of memory, while this value grows up to 100-150 MB as the window undergoes resizing. You will notice the memory is never released as the window is resized back to the starting size.

Our app should support window resizing on button press by the user. The memory occupied at the start is around 80-90 MB and it may grow up to 300-400 MB during the resizing.

This behaviour seems to be specific to Windows 11: we have carried out the same test on another PC with Windows 11 installed and the results are pretty similar.
On the contrary, by repeating the test on Windows 10, the memory always gets released as the resizing terminates.

This issue appears to be similar to QTBUG-91110 (though this was found on Windows 10).