Extended Product Grid with Editor

or search frequently asked questions:

How to add special price to Extended Product Grid?
Can I edit custom product attributes on the grid?
Is it possible to download/export the grid view?
Can different sets of columns be used by other admins?
Can the product quantity sold be displayed on the grid?
Can I add product attributes to the show on the Product Grid?
I need to filter products by category. Is that possible with your extension?
Can I set the order of columns?
How can I edit anything on the grid?