After the implementation of nested LLD rules it has become possible for prototypes to be discovered. These discovered prototypes, at some point in time, will no longer be discovered, and will be automatically deleted by an LLD rule, along with their parent LLD rule.
Currently, only the parent LLD rule has an info column, so it is the only place where You can check when this LLD rule will be automatically deleted, alongside with all of its prototypes.
Suggestion is to add an info column in the lists of discovered item/trigger/graph/host/LLD rule prototypes, so when the user navigates to those lists he would see an info icon in this column, and would know that all of these prototypes will be deleted together with their parent LLD.