What do you call a person that adds things to a list? [closed]

A "contributor" can be used for someone who contributes to the list.

Context is a factor here, of course. If you have a group of colleagues sitting around compiling a list of issues for their manager, each person adding an item to the list would have contributed to the list, thereby making them a contributor.

If a single person is responsible with the management of a list, you could say that person is keeping or managing the list. You could go ahead and call the person a list keeper or list manager.

If multiple persons can add items to a list, then you can say those who added items contributed to the list. They can be considered (list) contributors.

The most appropriate term is usually "editor":

editor — a person who edits material for publication, films, etc.

An editor will be responsible for adding, removing or updating items in a list.

There is no specific term for someone who only adds items to a list. You would have to use a term such as "the one who adds to the list". The closest term would be "compiler":

compiler — a person who compiles.

compiles — to put together (documents, selections, or other materials) in one book or work.

You can "compile a list" and someone who does this is a "compiler of lists". But this usually refers to the person who created the entire list -- not someone who simply added a few items here and there. That would be an "editor".