=LET(data,A1:H11,na,0,
s,SEQUENCE(COLUMNS(data)/2,,,2),
sh,TAKE(data,1),
dh,HSTACK(TAKE(sh,,1),CHOOSECOLS(sh,s+1)),
sd,DROP(data,1),
drl,SORT(UNIQUE(TOCOL(CHOOSECOLS(sd,s),1))),
dd,DROP(REDUCE("",s,LAMBDA(rr,c,
HSTACK(rr,XLOOKUP(drl,CHOOSECOLS(sd,c),
CHOOSECOLS(sd,c+1),na)))),,1),
VSTACK(dh,HSTACK(drl,dd)))