I am a novice in category theory, and I am studying the notion of Pro category. I wonder if the set $\operatorname{Hom}(0,0)$ only contains the identity morphism.
If it does not, since (I guess) any two morphisms in $\mathrm{Hom}(0,0)$ commute with respect to both the tensor product and the composition, as a consequence of the Eckmann-Hilton argument, is this the case with other morphisms ? More precisely, does a morphism $\mu$ in $\mathrm{Hom}(0,0)$ commute with a morphism $\mu'$ in $\mathrm{Hom}(n,m)$ with respect to the tensor product, i.e. $\mu\otimes\mu' = \mu' \otimes \mu$ ?
Moreover, is this the case for the the endomorphisms associated with the unit of any monoidal category?
Thank you all by advance !