Attributes are editable fields which will show up in your Addon settings on visual composer.
This is a short explenation of how to add attributes which your clients can using the the visual composer page builder.
Click on the "Attributes" tab.
Click on the "Add Attribute" button.
Choose the attribute type by selecting the relevant tab in the popup.
Fill in the fields: Title, Name and Default Value.
Click on the "Add Attribute" button to add the attribute.
Click the "HTML" tab.
And erase the html where you want your attribute to be replaced.
After erasing the html you want to replace, click on the attribute on the list in the left panel.
The attribute will show up in the HTML.
Click update to save.
Now the "H1" will show up as an editable field when you click on edit addon in the Visual Composer page builder.