How can I set the "Comment" field on Bill of Material items?

Summary:

We would like to set the "Comment" or "Description" field on Bill of Materiale items from the BOM Mapping Rule.

Content (required):

We are using an array table to add additional charges to a configuration, and from the BOM Mapping rule, we can set the Price [configurablePrice] on the Bill of Material items, but how can we set the “Comment” or the “Description” fields on the bill of material lines? - As is both fields gets the Pars Description value.

We have been looking all over for a tag/variable name for these two fields, but with no luck.