Drupal Commerce: line_item field in user profile? Im trying to achieve the add to favorites function, but I cant reference the commerce_product/product_display becose the items that are sold in my situation get customized by the user (add text, images, whatever).

I have a custom line item type called custom, where I added the field to handle the customization my users can do.

For the add to favorites functionality, i thought to add a line_item field in the user profile, put in it the custom line items created, and when he want to buy it all I have to do is create a new line item copying the fields value and then add it to the cart.

But i have some trouble: when i try to add (for test) the line items in the user's profile page throught the standard widget, I dont get any error message but the line items doesnt get saved..

Are them bounded to commerce_orders only?
Yes, I would not use a line item reference field outside of the order entity type. You might try using an entity reference field instead with the inline entity form module for line item creation / editing.