EpsExpand is an option for EpsEvaluate and other functions that use EpsEvaluate internally. When set to False, sums of momenta in the Eps tensor will not be rewritten as a sum of Eps tensors.
LC[mu, nu][q1 + q2, p1 + p2]
EpsEvaluate[%]\bar{\epsilon }^{\text{mu}\;\text{nu}\;\overline{\text{q1}}+\overline{\text{q2}}\;\overline{\text{p1}}+\overline{\text{p2}}}
-\bar{\epsilon }^{\text{mu}\;\text{nu}\;\overline{\text{p1}}\;\overline{\text{q1}}}-\bar{\epsilon }^{\text{mu}\;\text{nu}\;\overline{\text{p1}}\;\overline{\text{q2}}}-\bar{\epsilon }^{\text{mu}\;\text{nu}\;\overline{\text{p2}}\;\overline{\text{q1}}}-\bar{\epsilon }^{\text{mu}\;\text{nu}\;\overline{\text{p2}}\;\overline{\text{q2}}}
LC[mu, nu][q1 + q2, p1 + p2]
EpsEvaluate[%, EpsExpand -> False]\bar{\epsilon }^{\text{mu}\;\text{nu}\;\overline{\text{q1}}+\overline{\text{q2}}\;\overline{\text{p1}}+\overline{\text{p2}}}
-\bar{\epsilon }^{\text{mu}\;\text{nu}\;\overline{\text{p1}}+\overline{\text{p2}}\;\overline{\text{q1}}+\overline{\text{q2}}}