There are two extreme options in watchlists : either only the latest edit to pages are shown (default), or all edits are shown (expanded watchlist). It would make sense to have a middle ground, and be able to specify in options the number of already visited edits to each page that should be displayed on one's expanded watchlist.
If I choose 0, then only unvisited edits would be displayed, while if I choose 1, the last visited edit for each page would also be shown, and so on. When the option suggested in T76299 is enabled, a group of consecutive edits by a single user should count as one.