Some may already know about how to this, or have some software that already does it, but I figured it might be useful to share
Seems to work on android 10 and later (even on my old galaxy tab A 8.0)
Enable Developer options, scroll down and enable the force desktop/resizable options.
then open an application, and open the recent applications, long press on the icon at the top of the window you want to make float, and select pop-up-window
Now you have a little resizable window of the app, you can hit the minus (minimize) on the window to make it a floating bubble you can move around
Handy for making notes/etc