Is there an option to have a variable stored on site level instead of each placement of the component? So we could configure the default per site? Would we add a Design dialog for this case maybe?

[varunmitra]

Yes, this case happens to be a classic use case for design dialog.

With design dialog you can easily set the value once and have the same value rendered across your entire website. The value of your component would be stored underneath /etc/designs and would be static as long as the pages in your website refer to the same template and same design.

You can modify the design dialog value on any of the pages and changes would reflect across your entire site.