We plan to handle this by adding to your user page a list of your recently created serials that you don’t have a mark in.
We plan to provide both both “start from the beginning” and “start from the current page”. We have a different plan to handle new unscanned serials; we hope to scan them quickly enough that nobody other than the person who adds it notices, and we plan to show that person their recently created but unmarked serials.
As part of a project to clean up our listings, we now have an internal way to mark comics as “gone”, though there’s no UI yet. We have added a public “Report broken” button to the comic info pages though.