Do I need that fourth string?

Jessica Comeau says in her Dulcimer Lesson 1 to take it off, so I did. Then I watch Stephen Seifert demonstrating his Dulcimer School stuff and he has all 4 strings.

So, do I replace (and fix the action height) on that doubled melody string or leave it off?

I am considering learning to play with a pick, if that makes a difference.

I just made one today with a punch and lowered the action on the other 3 strings at the nut. (You could have flown a 747 under the strings before). It feels weird, but I’ll get it soon.