try:
=ARRAYFORMULA(TRIM({
IF(B!A2:A8<>""; 'C'!A2:A&" "&B!A2:A8; A!A2:A8)\
IF(B!B2:B8<>""; 'C'!B2:B&" "&B!B2:B8; A!B2:B8)\
IF(B!C2:C8<>""; 'C'!C2:C&" "&B!C2:C8; A!C2:C8)\
IF(B!D2:D8<>""; 'C'!D2:D&" "&B!D2:D8; A!D2:D8)\
IF(B!E2:E8<>""; 'C'!E2:E&" "&B!E2:E8; A!E2:E8)}))
, которое может быть просто:
=ARRAYFORMULA(TRIM(
IF(B!A2:E8<>""; 'C'!A2:E&" "&B!A2:E8; A!A2:E8)))