Hi,
The 70 group must have the bit 1.
Assuming dxfLst in the dxf list of an attrbute:
(entmod (subst (cons 70 (logior 1 (cdr (assoc 70 dxfLst)))) (assoc 70 dxfLst) dxfLst)
This works with an attribute reference (ATTRIB) or an attribute definition (ATTDEF) in the second case, to update all inserted references, you'd have to synchronize the attributes (ATTSYNC).