Terry is right, but the shorter version is that it saves me from having to write my response this way:
Find: ^.*?-
Replace: nothing
Search mode: Regular expression
. matches newline checkbox: Unchecked
As you can see, many less characters to type for me to simply use (?-s)
BTW, for those that don’t know, if the . matches newline box is checked, it effectively puts a (?s) at the start of whatever regular expression you supply in the Find what. So if your regular expression supplied is (?-s)^.*?- it becomes (?s)(?-s)^.*?- which is really just (?-s)^.*?- because the (?-s) part “undoes” what the leading (?s) does.