Alternatively with REDUCE and LAMBDA.
=DROP(REDUCE("",B2:B4,LAMBDA(u,v, VSTACK(u,VSTACK(v,FILTER(A7:A11,B7:B11=v), FILTER(A14:A18,ISNUMBER(XMATCH(B14:B18,FILTER(A7:A11,B7:B11=v)))))))),1)