How to minimize the app window (freeform mode/pop-up view)? I sometimes accidentally minimize the window for the app Quick Edit Pro, whilst working with it. I get the smaller variable size and position window that I can intentionally create for some apps by long press of the return button (Android 5, Samsung GN3).

But Quick Edit Pro does not appear in the list I get when long pressing the return button.

What kind of swiping movement do I sometimes perform unintentionally in the upper part of the screen, that minimizes the app to this useful window. (Going back to the full window is done by a simple button press.)

I have tried many times but can not repeat it intentionally.

I now find that it is called "freeform mode". I have not installed any special apps to enable it.
The phone in the question uses Android 5. I was now also using another phone with Android 6. In this version I stumbled over the answer by accident. This also works in my Android 5 phone.

You swipe diagonally from one upper corner. (If you don't hit a clean diagonal swipe, you will naturally risk getting a "settings"-screen or what the app in question does for horizontal swipe.



Click image for larger variant

Here it is called the gesture for "pop-up view".

(If I make the diagonal swipe for this app (SE), I get a red frame. It probably indicates that minimization of this app has been disabled.)