Using COUNTIF (?) to list missing training in scheduling spreadsheet

Thanks for the feedback and rep. . Glad to have helped.

Is in this case creating a seperate table an acceptable solution?

In that case plese try:

=LET(t,Table1,l,'Training lists'!B$3:B$5,n,INDEX(t,,1),d,DROP(t,,5),h,TAKE(Table1[#Headers],,5),b,TAKE(t,,4),
IFNA(REDUCE(h,SEQUENCE(ROWS(t)),LAMBDA(i,x,IF(INDEX(n,x)="",i,VSTACK(i,HSTACK(CHOOSEROWS(b,x),FILTER(l,ISNA(XMATCH(l,INDEX(d,x,))))))))),""))

See range A26:E36.