Link back panel core material to carcass core material

Link each back core material to its matching carcass core material in cabinet preferences so the back panel core applies by default across all cabinets.

1. To make a back panel core material apply by default across all cabinets, link the back core material to the corresponding carcass core material in cabinet preferences.

2. Setting the material in cabinet preferences alone may not apply it to all units; the core-to-core link must be configured.

3. The linking process is repeated for each carcass core material (e.g. 18mm BWP, BWR).