This doesn't look like PVCE adhesive although it is white in color and
it dries clear.  This looks to me like it might be a product called
E-600 or something similar.  I used to use this on the overlap in the
hinge area instead of hide glue.  There is a brand of epoxy called
"Foxy."  This epoxy dries to be very white in color.  Either way it
wouldn't be a "pretty picture."

You can try thin paint remover; I had success with that removing PVCE
adhesive.

Bill Maguire