Accessory subunit that is involved in the functional assembly of the mitochondrial respiratory chain complex I. Complex I has an NADH dehydrogenase activity with ubiquinone as an immediate electron acceptor and mediates the transfer of electrons from NADH to the respiratory chain. {ECO:0000269|PubMed:27626371, ECO:0000269|PubMed:28040730}. This is the function of NDUFB10 (NADH:ubiquinone oxidoreductase subunit B10, Ensembl gene identifier ENSG00000140990).