The series view inside your collection shows every issue from a specific series — what you own, what you're missing, and where the gaps are. Open it from any issue in your collection by choosing View Series, or from a series page using the collection indicator (appears when you own at least one issue from that series).
Issues are sorted by issue number (not date added), so you see your holdings in reading order.
Filtering#
The view lists every issue in the series by default, with the ones you own marked. Tick Missing only to hide those and leave just the gaps.
There is also a search box for finding a specific issue within a long run.
Missing only turns the view into a shopping list. PRO members can go further and use Bulk Add Missing Issues from here to fill the whole series at once.