In this talk we discuss some applications of the theory of conformal embeddings and
collapsing levels for affine vertex algebras developed in joint papers with Kac,
Moseneder, Papi,  Perse.
We present a proof of the semi-simplicity of the Kazhdan-Lusztig category KL of affine
vertex superalgebras at collapsing and some other levels. The proof uses the
representation theory of affine vertex algebras and concepts from the theory of
conformal embeddings. In the Lie superalgebra case, we discuss some examples when
KL_k has indecomposable highest weight modules and explains what is a possible
implication of this in the representation theory of vertex algebras. We will also discuss
relations of our results to vertex algebras with origins in some physics theories.