[openbox] How do I Alt+grab+drag?

[Luciano ES]

I have an old version of Debian where I've always been able to hold
the Alt key and grab any window and drag it around. I don't have to
click and hold any particular spot. Wherever the mouse pointer lands,
it works.

Then I tested FreeBSD some time ago and immediately noticed that this
Alt+dragging mechanism doesn't work.

Now I tested Debian Bullseye and it doesn't work either.

Why does it work in my old Debian and not in other systems? Where 
specifically is that configuration stored?

TIA

-- 
Luciano ES
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