Functions in xyloglucan synthesis by adding side chains to the xylosylated glucan backbone. Involved in galactosylating hemicellulose xyloglucan (XyG) at the second position of the XXXG motif to form XLXG (PubMed:22474179). Associates with other xyloglucan-synthesizing enzymes to form multiprotein complexes for xyloglucan synthesis in the Golgi (PubMed:25392066). Interacts with CSLC4, FUT1, XXT2 and XXT5. Expressed in roots, hypocotyls, cotyledons, leaves, stems and flowers. Belongs to the glycosyltransferase 47 family.