How to properly return a list item for editing?

I created a class for convenient creation of a list that consists of different types of objects with a single interface.

A list item is created by calling a class method, the result of the method is a newly created object in the list for EDIT.

While this code works, I'm not sure if it's safe to return a list item to edit properties?

If not, how can you safely return an element from the list so that you can edit it.

var builder = new ElementBuilder();
var item = builder.AddText("abc");

// Edit new reference element property, should be stored in "builder" variable
item.Bold = true;

.....

// Pass builder instance with added items to other place

// If we do something like this with added values on above
var x = builder.First();
Console.WriteLine(x.Text);
Console.WriteLine(x.Bold);

// Should output:
abc
true

public class ElementBuilder
{

    private List<IElement> elements;

    public TextElement AddText (string text)
    {
        var item = new TextElement (text);
        elements.Add(item);
        return _elements.First(x => x == item);
    }

    public ImageElement AddImage (string imageUrl)
    {
        var item = new ImageElement (imageUrl);
        elements.Add(item);
        return _elements.First(x => x == item);
    }

    .....
}