-- Module: Mathlib.CategoryTheory.Action.Concrete
Goal:
G : Type u_1
inst : Group G
H N : Subgroup G
inst_1 : Fintype (G ⧸ N)
inst_2 : Fintype (G ⧸ H)
h : N ≤ H
g : G
h₁ :
  ∀ (x : G ⧸ N),
    Eq (α := (fun (X : ObjectProperty.FullSubcategory Finite) ↦ X.obj) (V (ofMulAction G (FintypeCat.of (G ⧸ H)))))
      ((@ConcreteCategory.hom _ (ObjectProperty.FullSubcategory.category Finite)
              (fun (X Y : ObjectProperty.FullSubcategory Finite) ↦ TypeCat.Fun X.obj Y.obj)
              (fun (X : ObjectProperty.FullSubcategory Finite) ↦ X.obj)
              (fun (X Y : ObjectProperty.FullSubcategory Finite) ↦
                (TypeCat.instFunLikeFun : FunLike (TypeCat.Fun X.obj Y.obj) X.obj Y.obj))
              _ _ _
              (CategoryStruct.comp (Y := V (ofMulAction G (FintypeCat.of (G ⧸ N))))
                  ((ρ (ofMulAction G (FintypeCat.of (G ⧸ N))) : (a : G) → End (ofMulAction G (FintypeCat.of (G ⧸ N))).V)
                    g)
                  (FintypeCat.homMk (Quotient.lift (fun (x : G) ↦ ⟦x⟧) ⋯)) :
                V (ofMulAction G (FintypeCat.of (G ⧸ N))) ⟶ V (ofMulAction G (FintypeCat.of (G ⧸ H)))) :
            (a : (fun (X : ObjectProperty.FullSubcategory Finite) ↦ X.obj) (ofMulAction G (FintypeCat.of (G ⧸ N))).V) →
              (fun (X : ObjectProperty.FullSubcategory Finite) ↦ X.obj) (ofMulAction G (FintypeCat.of (G ⧸ H))).V)
          x :
        (fun (X : ObjectProperty.FullSubcategory Finite) ↦ X.obj) (V (ofMulAction G (FintypeCat.of (G ⧸ H)))))
      ((@ConcreteCategory.hom _ (ObjectProperty.FullSubcategory.category Finite)
              (fun (X Y : ObjectProperty.FullSubcategory Finite) ↦ TypeCat.Fun X.obj Y.obj)
              (fun (X : ObjectProperty.FullSubcategory Finite) ↦ X.obj)
              (fun (X Y : ObjectProperty.FullSubcategory Finite) ↦
                (TypeCat.instFunLikeFun : FunLike (TypeCat.Fun X.obj Y.obj) X.obj Y.obj))
              _ _ _
              (CategoryStruct.comp (Y := V (ofMulAction G (FintypeCat.of (G ⧸ H))))
                  (FintypeCat.homMk (Quotient.lift (fun (x : G) ↦ ⟦x⟧) ⋯))
                  ((ρ (ofMulAction G (FintypeCat.of (G ⧸ H))) : (a : G) → End (ofMulAction G (FintypeCat.of (G ⧸ H))).V)
                    g) :
                V (ofMulAction G (FintypeCat.of (G ⧸ N))) ⟶ V (ofMulAction G (FintypeCat.of (G ⧸ H)))) :
            (a : (fun (X : ObjectProperty.FullSubcategory Finite) ↦ X.obj) (ofMulAction G (FintypeCat.of (G ⧸ N))).V) →
              (fun (X : ObjectProperty.FullSubcategory Finite) ↦ X.obj) (ofMulAction G (FintypeCat.of (G ⧸ H))).V)
          x :
        (fun (X : ObjectProperty.FullSubcategory Finite) ↦ X.obj) (V (ofMulAction G (FintypeCat.of (G ⧸ H)))))
⊢ Eq.{u_1 + 1} (α := V (ofMulAction G (FintypeCat.of (G ⧸ N))) ⟶ V (ofMulAction G (FintypeCat.of (G ⧸ H))))
    (CategoryStruct.comp (Y := V (ofMulAction G (FintypeCat.of (G ⧸ N))))
      ((ρ (ofMulAction G (FintypeCat.of (G ⧸ N))) : (a : G) → End (ofMulAction G (FintypeCat.of (G ⧸ N))).V) g)
      (FintypeCat.homMk (Quotient.lift (fun (x : G) ↦ ⟦x⟧) ⋯)))
    (CategoryStruct.comp (Y := V (ofMulAction G (FintypeCat.of (G ⧸ H))))
      (FintypeCat.homMk (Quotient.lift (fun (x : G) ↦ ⟦x⟧) ⋯))
      ((ρ (ofMulAction G (FintypeCat.of (G ⧸ H))) : (a : G) → End (ofMulAction G (FintypeCat.of (G ⧸ H))).V) g))

Tactic:
ext (x : G ⧸ N)