There is an article linked right under the filter that explains why there are 4 letters A,B,H,K to represent letter repetition.
The pattern only works with specific positions inside the domain name. So just saying "remove all 3 letter...
It is not possible. You can use the "only Watchlist" filter in the list you want the end date for.
A watchlist domain can be in multiple different lists at the same time. Automatically picking "the right" end date to show is a mess. Easiest...