I recently ended up reformatting my computer and forgot to save my config file offline first. When I went to reset up my preferences, I've found that I now have multiple windows open where before it would only have a few open. I've checked everywhere and I can't figure out where that toggle is.

 

(Example: Opening the world map closed other windows such as inventory, abilities, etc. Same when doing field modification).

Ha, I knew I'd seen the setting before (tried it once but I actually prefer it with the limits so I set it back to how it was before) but it took me a minute or two of poking around in preferences to remember where I'd actually seen it. It is NOT anywhere in preferences. Open the interface editor instead and you'll see a checkbox for "enable movable secondary window". Aside from doing what it says, turning this on will also allow more windows to be open at the same time.