FeynCalcExternal[exp]
translates exp from the internal FeynCalc representation to a shorthand form.
[DiracGamma[5]] FeynCalcExternal
[DiracGamma[5]] // StandardForm
FeynCalcExternal
(*GA[5]*)
= {GA[\[Mu]], GAD[\[Rho]], GS[p], SP[p, q], MT[\[Alpha], \[Beta]], FV[p, \[Mu]]} ex
// StandardForm
ex
(*{GA[\[Mu]], GAD[\[Rho]], GS[p], SP[p, q], MT[\[Alpha], \[Beta]], FV[p, \[Mu]]}*)
// FeynCalcInternal ex
// FeynCalcInternal // StandardForm
ex
(*{DiracGamma[LorentzIndex[\[Mu]]], DiracGamma[LorentzIndex[\[Rho], D], D], DiracGamma[Momentum[p]], Pair[Momentum[p], Momentum[q]], Pair[LorentzIndex[\[Alpha]], LorentzIndex[\[Beta]]], Pair[LorentzIndex[\[Mu]], Momentum[p]]}*)
// FeynCalcInternal // FeynCalcExternal // StandardForm
ex
(*{GA[\[Mu]], GAD[\[Rho]], GS[p], SP[p, q], MT[\[Alpha], \[Beta]], FV[p, \[Mu]]}*)