[AFMUG] Power supplies in series

[TJ Trout]

I have 4 12v power supplies with isolated outputs that I plan to put in
series to make 48v but I was wondering is it possible to still connect to
only one or two while they are all in series to be able to draw 12, 24, and
48v? Or once they are on series you can't use anything but the total output
?