Starting with SOLIDWORKS 2018 you now have much more precise control over Linked Custom Properties in derived parts.
Previously, when creating a mirrored or derived part, it was possible to Transfer the Custom Properties from the source file to the new file that was being created. But it was an all or nothing operation, there was no way to control which properties would be transferred to the new file, all Custom Properties were transferred.
Once the Custom Properties were transferred to the new file, they were locked, “Linked to Parent Part”, so even if some of those properties should be different in the derived part file, there was no way to modify them.
Now in SOLIDWORKS 2018 however, we have individual control over each of the Linked Custom Properties that is transferred by this operation. This is possible because of the new “Linked” column.
To edit an individual Custom Property, just uncheck the checkbox in the “Linked” column. Once this is unchecked, the “Value/Text Expression” field can be edited.
Unfortunately, this new functionality ONLY works with files created in SOLIDWORKS 2018. The source can be an existing file created in a previous release, but the mirrored or derived part must be created in SOLIDWORKS 2018 for the new “Linked” check box to be available.