This is very handy when some of the menu choices won’t fit in that window. I used to do that by holding Alt and drag the menu. But it’s no longer working. I tried emulating the Num pad and/or the middle mouse button, as I used to use those before, but still no luck 
Shift + MiddleMouseDrag works for me
You can also just scroll:
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Perhaps you’re thinking of window edge dragging?
If you RMB a window edge, you also get a few other window options.
Official documentation is also always available relating to other window options.
https://docs.blender.org/manual/en/latest/interface/window_system/areas.html
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