Limbo is a realm of hell, and thus, pan-dimensional.
What makes Limbo different than the other hells to get a separate page in this website is the fact that Limbo is connected to the crossroads of Infinity.
Even Doctor Strange's illusion spell is said to not be able to last long against Limbo creatures.
Now, outside of hell Limbo, Marvel contains another limbo known as Comic Book Limbo which holds fictions and comics, even marvel comics which are forgotten (retconned)
TOAA later also confirms the existence of this realm by saying "nothing that is made is ever lost"
