To avoid Catastrophic failure, we check max sag and Compare it with given project specific Max allowable Sag as B31.3 don't talk about Allowable Sagging.

Can We have deflection value(sag) at midpoint by default in displacement summary? (C-II only checks at end node points of piping element. But in case of small bore critical lines with higher span, max sag check will not highlighted).

Can we have Red/Black Check for sagging by providing limiting value in .cfg File as like we do check stress Summary.

This isn't something we can provide in a week or two. If you need this information now, use smaller element lengths in your model (more nodes). If you have an existing model with longer spans where you're concerned about the sag, use the [Break] command to automatically break the span into smaller elements.