How to flag a product variation on a commerce website?
I wrote a way to use Flag for product variations here: http://drupal.org/node/1911568

Here is my solution:


Add a flag "add to wishlist" for commerce_product entity type.
Install computed field module.
Add a computed field to the product (not the display content type)
In Display Code (PHP) area of the field:

$entity_id = array_shift(entity_extract_ids($entity_type,$entity));
$display_output = flag_create_link('add_to_wishlist', $entity_id);


(Computed Code (PHP) part can be left empty, we dont want to store anything in database)
5. Go to Manage Display of the product and set the newly created computed field's format: "unsanitized" and make sure it is visible.
6. Go to Manage Display of the product display content type (not the product) and use your product's wishlist computed field there.

Now you can create a view to display a user's products in his wishlist. It is straitforward. You just add any field, add a relation: your flag and tweak the view as you like. You can also use view's menu system to create tabs on the user profile: http://drupal.org/node/326580