proposition: Lemma disp_tensor_with_id_left {C : category} {D : disp_cat C} {M : monoidal C} (DM : disp_monoidal D M) {x y z : C} {f : z --> y} {g : y --> z} (p : g · f = identity y) (xx : D x) (yy : D y) : xx ⊗⊗^{DM}_{l} transportb (mor_disp _ _) p (id_disp yy) = transportb _ (maponpaths (λ i, x ⊗^{M}_{l} i) p @ bifunctor_leftid M x y) (id_disp (xx ⊗⊗_{DM} yy)).
proof: Proof. set (pp := disp_tensor_distributes_over_transportb_right DM p xx (transportb _ p (id_disp yy)) (id_disp yy) (idpath _)). rewrite <- transport_b_b. etrans. 2: { apply maponpaths. apply (disp_bifunctor_leftid DM _ _ xx yy). } refine (_ @ pp). apply maponpaths. now rewrite transportb_const. Qed.
imports: UniMath.Foundations.All UniMath.MoreFoundations.All UniMath.CategoryTheory.Core.Categories UniMath.CategoryTheory.Core.Functors UniMath.CategoryTheory.Core.Isos UniMath.CategoryTheory.Core.NaturalTransformations UniMath.CategoryTheory.Monoidal.WhiskeredBifunctors UniMath.CategoryTheory.Monoidal.Categories UniMath.CategoryTheory.Monoidal.Displayed.WhiskeredDisplayedBifunctors UniMath.CategoryTheory.DisplayedCats.Core UniMath.CategoryTheory.DisplayedCats.Functors UniMath.CategoryTheory.DisplayedCats.Constructions UniMath.CategoryTheory.DisplayedCats.Isos UniMath.CategoryTheory.DisplayedCats.NaturalTransformations UniMath.CategoryTheory.Monoidal.Displayed.Monoidal