In-line editing, display at the top or the bottom of a list?

I'm working with a nested list view. In order to add data to the list, the user initially sees an "add" button. Clicking this add button prompts a search bar where the user can then search for the desired content to make additions to their list.

My question here is, should the add button/search bar be at the top or the bottom of the list?

Aesthetically, I like the add/search to display at the bottom because then the results never overlap the list and additions are pushed to the bottom. However, what happens when the user has a long list? They would likely have to scroll down to the bottom to find the add button.

Another question to consider is if I do implement the add/search at the top, would it make better sense for the additions to push to the top of the list or the bottom?