How to make reference Characteristics to another table, different from Class Type assignment?

Good day, professionals!

The user required to see Vendor Email in Vendor characteristics, for information purposes. I want to add an additional characteristics to the existing vendor class and set the following determination logic for it - pick ADRNR from LFA1, transfer to ADR6-ADDRNUMBER, and retrieve ADR6-SMTP_ADDR(E-mail number) as Characteristics Value.

Is such requirement feasible at all? If yes, what customizing should I use to implement it?

What I tried to do for now:

I created a reference characteristics and assigned it to the field from Address table (ADR6-SMTP_ADDR)

Then I tried to add new characteristics to the existing vendor class of class type 010 through CL02, and got the following error:

"Characteristic TEST_VENDOR_EMAIL is not a reference characteristic in class type 010

Message no. CL061"

When I checked the customizing table TCLA, I see that assignment "Class type - table" is "010-LFA1"

How to make an additional entry of "010-ADR6"? Or may be I'm doing it wrong, and I should choose another way?