For example , if I want to list only unseen/unread emails? I know you can use some sort of expressions when doing a search with / but not sure what is supported. Am I able to specify a flag based search for example?
Sounds like you're looking for the "limit" command. E.g. type "
l~U" (that starts with an ell for "limit", not a 1 or an I....) to get all unread
Update: I've fixed this to use "U" for Unread, rather than "N" for New.