Is your feature request related to a problem? Please describe.

I have a customer, who is:

• creating orders manually using the backend
• adding products using the SKU for search
• Adding only one SKU (at product level) for variable products
  • no extra SKU for each variation

The problem

• Variations are not found, when using the SKU within the search dialog.
• but the parent SKU is shown as placeholder in each variation, which implies, that this is also the SKU for the variation

Describe the solution you'd like

Also show variations using the SKU of the "parent" product for search.