The ideia is quite simple and I think it's obrigatory to have implemented!
When we have symmetry constrain in our assembly it uses 3 componentes although only the ones that are symmetric will show the constrain in the model tree, my suggestion is to show it also in the component that is the middle plane.
Sometimes I'm trying to see why I can't move something and I don't instantaneously see that that component is being used in a symmetric constrain.
I know that I can see it if I click on that component and show the constrains but as you can see there is an inconsistency in the approach why are they visible in one place but not in the other??