Product variant &1 not supported for the composition group &2

What causes this issue?

In the product structure, there is a composition group that has objects
with assigned product variants that are not supported by this
composition group.

System Response

Some content displayed in the structure may be doubled because it is not
grouped by the product variants.

How to fix this error?

Configure the customizing entries for the composition groups in the
Customizing activity <LS>Product Compliance for Discrete Industries ->
General Configuration -> Product and Specification Database -> Specify
Composition Groups and Product Variants</>.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.