From the package documentation (page 7):
7 Several floats per page
\efloatseparator
Endfloat places
\efloatseparator after each float in their respective files. By de-
fault it is defined to be \clearpage forcing one float per page. You
may change this by using \renewcommand to redefine \efloatseparator as
you wish. One possibility, suggested by a user, is
\renewcommand{\efloatseparator}{\mbox{}}
It makes most sense to place
such a redefinition in the configuration file (see section 8).
Do not
be mislead by my misleading name for this command. This actually
appears after each float including the last one, so is not truly a
separator.
Do note that this package is not intended to be used in preparing the final, published version of a document. It is not supposed to make the document user-friendly or readable. It is designed to format the document temporarily into a form which journals want. The journals do not publish articles in this format. Nor should you.